THE journey back to Airlee lasted almost three days---partly because Alvin, for his own reasons, was in no hurry to return. The physical exploration of Lys had now taken second place to a more important and exciting project; he was slowly making contact with the strange, obsessed intelligence which had now become his companion.

He suspected that the robot was trying to use him for its own purposes, which would be no more than poetic justice. What its motives were he could never be quite certain, since it still stubbornly refused to speak to him. For some reason of his own---perhaps fear that it might reveal too many of his secrets---the Master must have placed very efficient blocks upon its speech circuits, and Alvin's attempts to clear them were completely unsuccessful. Even indirect questioning of the "If you say nothing I shall assume you mean 'Yes'" type failed; the robot was much too intelligent to be taken in by such simple tricks.

In other respects, however, it was more co-operative. It would obey any orders that did not require it to speak or reveal information. After a while Alvin found that he could control it, as he could direct the robots in Diaspar, by thought alone. This was a great step forward, and a little later the creature---it was hard to think of it as a mere machine---relaxed its guard still further and allowed him to see through its eyes. It did not object, it seemed, to such passive forms of communication, but it blocked all attempts at closer intimacy.

Hilvar's existence it ignored completely; it would obey none of his commands, and its mind was closed to all his probing. At first this was something of a disappointment to Alvin, who had hoped that Hilvar's greater mental powers would enable him to force open this treasure chest of hidden memories. It was not until later that he realized the advantage of possessing a servant who would obey no one else in all the world.

The member of the expedition who strongly objected to the robot was Krif. Perhaps he imagined that he now had a rival, or perhaps he disapproved, on general principles, of anything that flew without wings. When no one was looking, he had made several direct assaults on the robot, which had infuriated him still further by taking not the slightest notice of his attacks. Eventually Hilvar had been able to calm him down, and on the homeward journey in the ground-car he seemed to have resigned himself to the situation. Robot and insect escorted the vehicle as it glided silently through forest and field---each keeping to the side of its respective master and pretending that its rival was not there.

Seranis was already waiting for them as the car floated into Airlee. It was impossible, Alvin thought, to surprise these people. Their interlinked minds kept them in touch with everything that was happening in their land. He wondered how they had reacted to his adventures in Shalmirane, which presumably everyone in Lys now knew about.

Seranis seemed to be worried and more uncertain than he had ever seen her before, and Alvin remembered the choice that now lay before him. In the excitement of the last few days he had almost forgotten it; he did not like to spend energy worrying about problems that still lay in the future. But the future was now upon him; he must decide in which of these two worlds he wished to live.

The voice of Seranis was troubled when she began to speak, and Alvin had the sudden impression that something had gone awry with the plans that Lys had been making for him. What had been happening during his absence? Had emissaries gone into Diaspar to tamper with Khedron's mind---and had they failed in their duty?

"Alvin," began Seranis, "there are many things I did not tell you before, but which you must now learn if you are to understand our actions.

"You know one of the reasons for the isolation of our two races. The fear of the Invaders, that dark shadow in the depths of every human mind, turned your people against the world and made them lose themselves in their own dreams. Here in Lys that fear has never been so great, though we bore the burden of the final attack. We had a better reason for our actions, and what we did, we did with open eyes.

"Long ago, Alvin, men sought immortality and at last achieved it. They forgot that a world which had banished death must also banish life. The power to extend his life indefinitely might bring contentment to the individual, but brought stagnation to the race. Ages ago we sacrificed our immortality, but Diaspar still follows the false dream. That is why our ways parted---and why they must never meet again."

Although the words had been more than half expected, the blow seemed none the less for its anticipation. Yet Alvin refused to admit the failure of all his plans---half-formed though they were---and only part of his brain was listening to Seranis now. He understood and noted all her words, but the conscious portion of his mind was retracing the road to Diaspar, trying to imagine every obstacle that could be placed in his way.

Seranis was clearly unhappy. Her voice was almost pleading as it spoke, and Alvin knew that she was talking not only to him but to her son. She must be aware of the understanding and affection that had grown up between them during the days they had spent together. Hilvar was watching his mother intently as she spoke, and it seemed to Alvin that his gaze held not merely concern but also more than a trace of censure.

"We do not wish to make you do anything against your will, but you must surely realize what it would mean if our people met again. Between our culture and yours is a gulf as great as any that ever separated Earth from its ancient colonies. Think of this one fact, Alvin. You and Hilvar are now of nearly the same age---but both he and I will have been dead for centuries while you are still a youth. And this is only your first in an infinite series of lives."

The room was very quiet, so quiet that Alvin could hear the strange, plaintive cries of unknown beasts in the fields beyond the village. Presently, he said, almost in a whisper: "What do you want me to do?"

"We hoped that we could give you the choice of staying here or returning to Diaspar, but now that is impossible. Too much has happened for us to leave the decision in your hands. Even in the short time you have been here, your influence has been highly disturbing. No, I am not reproving you; I am sure you intended no harm. But it would have been best to leave the creatures you met in Shalmirane to their own destiny.

"And as for Diaspar----" Seranis gave a gesture of annoyance. "Too many people know where you have gone; we did not act in time. What is most serious, the man who helped you discover Lys has vanished; neither your Council nor our agents can discover him, so he remains a potential danger to our security. Perhaps you are surprised that I am telling you all this, but it is quite safe for me to do so. I am afraid we have only one choice before us; we must send you back to Diaspar with a false set of memories. Those memories have been constructed with great care, and when you return home you will know nothing of us. You will believe that you have had rather dull and dangerous adventures in gloomy underground caverns, where the roofs continually collapsed behind you and you kept alive only through eating unappetizing weeds and drinking from occasional springs. For the rest of your life you will believe this to be the truth, and everyone in Diaspar will accept your story. There will be no mystery, then, to lure any future explorers; they will think they know all there is to be known about Lys."

Seranis paused and looked at Alvin with anxious eyes. "We are very sorry that this is necessary and ask your forgiveness while you still remember us. You may not accept our verdict, but we know many facts that are hidden from you. At least you will have no regrets, for you will believe that you have discovered all that there is to be found."

Alvin wondered if that was true. He was not sure that he would ever settle down to the routine of life in Diaspar, even when he had convinced himself that nothing worthwhile existed beyond its walls. What was more, he had no intention of putting the matter to the test.

"When do you wish me to undergo this---treatment?" Alvin asked.

"Immediately. We are ready now. Open your mind to me, as you did before, and you will know nothing until you find yourself back in Diaspar."

Alvin was silent for a while. Then he said quietly: "I would like to say good-bye to Hilvar."

Seranis nodded.

"I understand. I will leave you here for a while and return when you are ready." She walked over to the stairs that led down to the interior of the house, and left them alone on the roof.

It was some time before Alvin spoke to his friend; he felt a great sadness, yet also an unbroken determination not to permit the wreck of all his hopes. He looked once more down upon the village where he had found a measure of happiness and which he might never see again if those who were ranged behind Seranis had their way. The ground-car was still standing beneath one of the wide-branching trees, with the patient robot hanging in the air above it. A few children had gathered around to examine this strange newcomer, but none of the adults seemed in the least interested.

"Hilvar," said Alvin abruptly, "I'm very sorry about this."

"So am I," Hilvar answered, his voice unstable with emotion. "I had hoped that you could have remained here."

"Do you think that what Seranis wants to do is right?"

"Do not blame my mother. She is only doing as she is asked," replied Hilvar. Though he had not answered his question, Alvin had not the heart to ask it again. It was unfair to put such a strain on his friend's loyalty.

"Then tell me this," asked Alvin, "how could your people stop me if I tried to leave with my memories untouched?"

"It would be easy. If you tried to escape, we would take control of your mind and force you to come back."

Alvin had expected as much and was not discouraged. He wished that he could confide in Hilvar, who was obviously upset by their impending separation, but he dared not risk the failure of his plans. Very carefully, checking every detail, he traced out the only road that could lead him back to Diaspar on the terms he wished.

There was one risk which he had to face, and against which he could do nothing to protect himself. If Seranis broke her promise and dipped into his mind, all his careful preparations might be in vain.

He held out his hand to Hilvar, who grasped it firmly but seemed unable to speak.

"Let's go downstairs to meet Seranis," said Alvin. "I'd like to see some of the people in the village before I go."

Hilvar followed him silently into the peaceful coolness of the house and then out through the hallway and onto the ring of coloured glass that surrounded the building. Seranis was waiting for them there, looking calm and resolute. She knew that Alvin was trying to hide something from her, and thought again of the precautions she had taken. As a man may flex his muscles before some great effort, she ran through the compulsion patterns she might have to use.

"Are you ready, Alvin?" she asked.

"Quite ready," replied Alvin, and there was a tone in his voice that made her look at him sharply.

"Then it will be best if you make your mind a blank, as you did before. You will feel and know nothing after that, until you find yourself back in Diaspar."

Alvin turned to Hilvar and said in a quick whisper that Seranis could not hear: "Good-bye, Hilvar, Don't worry---I'll be back." Then he faced Seranis again.

"I don't resent what you are trying to do," he said. "No doubt you believe it is for the best, but I think you are wrong. Diaspar and Lys should not remain apart forever; one day they may need each other desperately. So I am going home with all that I have learned---and I do not think that you can stop me."

He waited no longer, and it was just as well. Seranis never moved, but instantly he felt his body slipping from his control. The power that had brushed aside his own will was even greater than he had expected, and he realized that many hidden minds must be aiding Seranis. Helplessly he began to walk back into the house, and for an awful moment he thought his plan had failed.

Then there came a flash of steel and crystal, and metal arms closed swiftly around him. His body fought against them, as he had known that it must do, but the struggles were useless. The ground fell away beneath him and he caught a glimpse of Hilvar, frozen by surprise, with a foolish smile upon his face.

The robot was carrying him a dozen feet above the ground, much faster than a man could run. It took Seranis only a moment to understand his ruse, and his struggles died away as she relaxed her control. But she was not defeated yet, and presently there happened that which Alvin had feared and done his best to counteract.

There were now two separate entities fighting inside his mind, and one of them was pleading with the robot, begging it to set him down. The real Alvin waited, breathlessly, resisting only a little against forces he knew he could not hope to fight. He had gambled; there was no way of telling beforehand if his uncertainty would obey orders as complex as those that he had given it. Under no circumstances, he had told the robot, must it obey any further commands of his until he was safely inside Diaspar. Those were the orders. If they were obeyed, Alvin had placed his fate beyond the reach of human interference.

Never hesitating, the machine raced on along the path he had so carefully mapped out for it. A part of him was still pleading angrily to be released, but he knew now that he was safe. And presently Seranis understood that too, for the forces inside his brain ceased to war with one another. Once more he was at peace, as ages ago an earlier wanderer had been when, lashed to the mast of his ship, he had heard the song of the Sirens die away across the wine-dark sea.

THE Master had come to earth amid the chaos of the Transition Centuries, when the Galactic Empire was crumbling but the lines of communication among the stars had not yet completely broken. He had been of human origin, though his home was a planet circling one of the Seven Suns. While still a young man, he had been forced to leave his native world, and its memory had haunted him all his life. His expulsion he blamed on vindictive enemies, but the fact was that he suffered from an incurable malady which, it seemed, attacked only Homo sapiens among all the intelligent races of the Universe. That disease was religious mania.

Throughout the earlier part of its history, the human race had brought forth an endless succession of prophets, seers, messiahs, and evangelists who convinced themselves and their followers that to them alone were the secrets of the Universe revealed. Some of them succeeded in establishing religions that survived for many generations and influenced billions of men; others were forgotten even before their deaths.

The rise of science, which with monotonous regularity refuted the cosmologies of the prophets and produced miracles which they could never match, eventually destroyed all these faiths. It did not destroy the awe, nor the reverence and humility, which all intelligent beings felt as they contemplated the stupendous Universe in which they found themselves. What it did weaken, and finally obliterate, were the countless religions, each of which claimed with unbelievable arrogance that it was the sole repository of the truth and that its millions of rivals and predecessors were all mistaken.

Yet, though they never possessed any real power once humanity had reached a very elementary level of civilization, all down the ages isolated cults had continued to appear, and however fantastic their creeds they had always managed to attract some disciples. They thrived with particular strength during periods of confusion and disorder, and it was not surprising that the Transition Centuries had seen a great outburst of irrationality. When reality was depressing, men tried to console themselves with myths.

The Master, even if he was expelled from his own world, did not leave it unprovided. The Seven Suns had been the centre of galactic power and science, and he must have possessed influential friends. He had made his hegira in a small but speedy ship, reputed to be one of the fastest ever built. With him into exile he had taken another of the ultimate products of galactic science---the robot that was looking at Alvin and Hilvar even now.

No one had ever known the full talents and functions of this machine. To some extent, indeed, it had become the Master's alter ego; without it, the religion of the Great Ones would probably have collapsed after the Master's death. Together they had roved among the star clouds on a zigzag trail which led at last, certainly not by accident, back to the world from which the Master's ancestors had sprung.

Entire libraries had been written about that saga, each work therein inspiring a host of commentaries until, by a kind of chain reaction, the original volumes were lost beneath mountains of exegesis and annotation. The Master had stopped at many worlds, and made disciples among many races. His personality must have been an immensely powerful one for it to have inspired humans and non-humans alike, and there was no doubt that a religion of such wide appeal must have contained much that was fine and noble. Probably the Master was the most successful---as he was also the last---of all mankind's messiahs. None of his predecessors could have won so many converts or had their teachings carried across such gulfs of time and space.

What those teachings were neither Alvin nor Hilvar could ever discover with any accuracy. The great polyp did its desperate best to convey them, but many of the words it used were meaningless and it had a habit of repeating sentences or whole speeches with a kind of swift mechanical delivery that made them very hard to follow. After a while Hilvar did his best to steer the conversation away from these meaningless morasses of theology in order to concentrate on ascertainable facts.

The Master and a band of his most faithful followers had arrived on Earth in the days before the cities had passed away, and while the Port of Diaspar was still open to the stars. They must have come in ships of many kinds; the polyps, for example, in one filled with the waters of the sea which was their natural home. Whether the movement was well received on Earth was not certain; but at least it met no violent opposition, and after further wanderings it set up its final retreat among the forests and mountains of Lys.

At the close of his long life, the Master's thoughts had turned once more toward the home from which he had been exiled, and he had asked his friends to carry him out into the open so that he could watch the stars. He had waited, his strength waning, until the culmination of the Seven Suns, and toward the end he babbled many things which were to inspire yet more libraries of interpretation in future ages. Again and again he spoke of the "Great Ones" who had now left this universe of space and matter but who would surely one day return, and he charged his followers to remain to greet them when they came. Those were his last rational words. He was never again conscious of his surroundings, but just before the end he uttered one phrase that had come down the ages to haunt the minds of all who heard it: "It is lovely to watch the coloured shadows on the planets of eternal light." Then he died.

At the Master's death, many of his followers broke away, but others remained faithful to his teachings, which they slowly elaborated through the ages. At first they believed that the Great Ones, whoever they were, would soon return, but that hope faded with the passing centuries. The story here grew very confused, and it seemed that truth and legend were inextricably intertwined. Alvin had only a vague picture of generations of fanatics, waiting for some great event which they did not understand to take place at some unknown future date.

The Great Ones never returned. Slowly the power of the movement failed as death and disillusion robbed it of its disciples. The short-lived human followers were the first to go, and there was something supremely ironic in the fact that the very last adherent of a human prophet was a creature utterly unlike Man.

The great polyp had become the Master's last disciple for a very simple reason. It was immortal. The billions of individual cells from which its body was built would die, but before that happened they would have reproduced themselves. At long intervals the monster would disintegrate into its myriad separate cells, which would go their own way and multiply by fission if their environment was suitable. During this phase the polyp did not exist as a self-conscious, intelligent entity---here Alvin was irresistibly reminded of the manner in which the inhabitants of Diaspar spent their quiescent millenniums in the city's Memory Banks.

In due time some mysterious biological force brought the scattered components together again, and the polyp began a new cycle of existence. It returned to awareness and recollected its earlier lives, though often imperfectly since accident sometimes damaged the cells that carried the delicate patterns of memory.

Perhaps no other form of life could have kept faith so long to a creed otherwise forgotten for a billion years. In a sense, the great polyp was a helpless victim of its biological nature. Because of its immortality, it could not change, but was forced to repeat eternally the same invariant pattern.

The religion of the Great Ones, in its later stages, had become identified with a veneration of the Seven Suns. When the Great Ones stubbornly refused to appear, attempts were made to signal their distant home. Long ago the signaling had become no more than a meaningless ritual, now maintained by an animal that had forgotten how to learn and a robot that had never known how to forget.

As the immeasurably ancient voice died away into the still air, Alvin found himself overwhelmed by a surge of pity. The misplaced devotion, the loyalty that had held to its futile course while suns and planets passed away---he could never have believed such a tale had he not seen the evidence before his eyes. More than ever before the extent of his ignorance saddened him. A tiny fragment of the past had been illuminated for a little while, but now the darkness had closed over it again.

The history of the Universe must be a mass of such disconnected threads, and no one could say which were important and which were trivial. This fantastic tale of the Master and the Great Ones seemed like another of the countless legends that had somehow survived from the civilizations of the Dawn. Yet the very existence of the huge polyp, and of the silently watching robot, made it impossible for Alvin to dismiss the whole story as a fable built of self-delusion upon a foundation of madness.

What was the relationship, he wondered, between these two entities, which though so different in every possible way had maintained their extraordinary partnership over such aeons of time? He was somehow certain that the robot was much the more important of the two. It had been the confidant of the Master and must still know all his secrets.

Alvin looked at the enigmatic machine that still regarded him so steadily. Why would it not speak? What thoughts were passing through its complicated and perhaps alien mind? Yet, surely, if it had been designed to serve the Master, its mind would not be altogether alien, and it should respond to human orders.

As he thought of all the secrets which that stubbornly mute machine must possess, Alvin felt a curiosity so great that it verged upon greed. It seemed unfair that such knowledge should be wasted and hidden from the world; here must lie wonders beyond even the ken of the Central Computer in Diaspar.

"Why won't your robot speak to us?" he asked the polyp, when Hilvar had momentarily run out of questions. The answer was one he had half expected.

"It was against the Master's wishes for it to speak with any voice but his, and his voice is silent now."

"But it will obey you?"

"Yes; the Master placed it in our charge. We can see through its eyes, wherever it goes. It watches over the machines that preserve this lake and keep its water pure. Yet it would be truer to call it our partner than our servant."

Alvin thought this over. An idea, still vague and half- formed, was beginning to take shape in his mind. Perhaps it was inspired by pure lust for knowledge and power; when he looked back on this moment he could never be certain just what his motives were. They might be largely selfish, but they also contained some element of compassion. If he could do so, he would like to break this futile sequence and release these creatures from their fantastic fate. He was not sure what could be done about the polyp, but it might be possible to cure the robot of its insanity and at the same time to release its priceless, pent-up memories.

"Are you certain," he said slowly, talking to the polyp but aiming his words at the robot, "that you are really carrying out the Master's wishes by remaining here? He desired the world to know of his teachings, but they have been lost while you hide here in Shalmirane. It was only by chance that we discovered you, and there may be many others who would like to hear the doctrine of the Great Ones."

Hilvar glanced at him sharply, obviously uncertain of his intentions. The polyp seemed agitated, and the steady beating of its respiratory equipment faltered for a few seconds. Then it replied, in a voice not altogether under control: "We have discussed this problem for many years. But we cannot leave Shalmirane, so the world must come to us, no matter how long it takes."

"I have a better idea," said Alvin eagerly, "it is true that you may have to stay here in the lake, but there is no reason why your companion should not come with us. He can return whenever he wishes or whenever you need him. Many things have changed since the Master died---things which you should know about, but which you can never understand if you stay here."

The robot never moved, but in its agony of indecision the polyp sank completely below the surface of the lake and remained there for several minutes. Perhaps it was having a soundless argument with its colleague; several times it began to re-emerge; thought better of it, and sank into the water again. Hilvar took this opportunity to exchange a few words with Alvin.

"I'd like to know what you are trying to do," he said softly, his voice half-bantering and half-serious. "Or don't you know yourself?"

"Surely," replied Alvin, "you feel sorry for these poor creatures? Don't you think it would be a kindness to rescue them?"

"I do, but I've learned enough about you to be fairly certain that altruism isn't one of your dominant emotions. You must have some other motive."

Alvin smiled ruefully. Even if Hilvar did not read his mind---and he had no reason to suppose that he did---he could undoubtedly read his character.

"Your people have remarkable mental powers," he replied, trying to divert the conversation from dangerous ground. "I think they might be able to do something for the robot, if not this animal." He spoke very softly, lest he be overheard. The precaution might have been a useless one, but if the robot did intercept his remarks it gave no sign of it.

Fortunately, before Hilvar could press the inquiry any further, the polyp emerged once more from the lake. In the last few minutes it had become a good deal smaller and its movements were more disorganized. Even as Alvin watched, a segment of its complex, translucent body broke away from the main bulk and then disintegrated into multitudes of smaller sections, which swiftly dispersed. The creature was beginning to break up before their eyes.

Its voice, when it spoke again, was very erratic and hard to understand.

"Next cycle starting," it jerked out in a kind of fluctuating whisper. "Did not expect it so soon---only few minutes left---stimulation too great---cannot hold together much longer."

Alvin and Hilvar stared at the creature in horrified fascination. Even though the process they were watching was a natural one, it was not pleasant to watch an intelligent creature apparently in its death throes. They also felt an obscure sense of guilt; it was irrational to have the feeling, since it was of no great importance when the polyp began another cycle, but they realized that the unusual effort and excitement caused by their presence was responsible for this premature metamorphosis.

Alvin realized that he would have to act quickly or his op- THE CITY AND THE STARS 151 portunity would be gone—perhaps only for a few years, per- haps for centuries.

"What have you decided?" he said eagerly. "Is the robot coming with us?"

There was an agonizing pause while the polyp tried to force its dissolving body to obey its will. The speech diaphragm fluttered, but no audible sound came from it. Then, as if in a despairing gesture of farewell, it waved its delicate palps feebly and let them fall back into the water, where they promptly broke adrift and went floating out into the lake. In a matter of minutes, the transformation was over. Nothing of the creature larger than an inch across remained. The water was full of tiny, greenish specks, which seemed to have a life and mobility of their own and which rapidly disappeared into the vastness of the lake.

The ripples on the surface had now altogether died away, and Alvin knew that the steady pulse beat that had sounded in the depths would now be stilled. The lake was dead again---or so it seemed. But that was an illusion; one day the unknown forces that had never failed to do their duty in the past would exert themselves again, and the polyp would be reborn. It was a strange and wonderful phenomenon, yet was it so much stranger than the organization of the human body, itself a vast colony of separate, living cells?

Alvin wasted little effort on such speculations. He was oppressed by his sense of failure, even though he had never clearly conceived the goal he was aiming for. A dazzling opportunity had been missed and might never again return. He stared sadly out across the lake, and it was some time before his mind registered the message which Hilvar was speaking quietly in his ear.

"Alvin," his friend said softly, "I think you have won your point."

He spun swiftly on his heels. The robot, which until now had been floating aloofly in the distance, never approaching within twenty feet of them, had moved up in silence and was now poised a yard above his head. Its unmoving eyes, with their wide angles of vision, gave no indication of its direction of interest. Probably it saw the entire hemisphere in front of it with equal clarity, but Alvin had little doubt that its attention was now focused upon him.

It was waiting for his next move. To some extent, at least, it was now under his control. It might follow him to Lys, perhaps even to Diaspar---unless it changed its mind. Until then, he was its probationary master.

THE night was at its deepest when Alvin woke. Something had disturbed him, some whisper of sound that had crept into his mind despite the endless thunder of the falls. He sat up in the darkness, straining his eyes across the hidden land, while with indrawn breath he listened to the drumming roar of the water and the softer, more fugitive sounds of the creatures of the night.

Nothing was visible. The starlight was too dim to reveal the miles of country that lay hundreds of feet below; only a jagged line of darker night eclipsing the stars told of the mountains on the southern horizon. In the darkness beside him Alvin heard his companion roll over and sit up.

"What is it?" came a whispered voice.

"I thought I heard a noise."

"What sort of noise?"

"I don't know: perhaps it was just imagination."

There was a silence while two pairs of eyes peered out into the mystery of the night. Then, suddenly, Hilvar caught Alvin's arm.

"Look!" he whispered.

Far to the south glowed a solitary point of light, too low in the heavens to be a star. It was a brilliant white, tinged with violet, and even as they watched it began to climb the spectrum of intensity, until the eye could no longer bear to look upon it. Then it exploded---and it seemed as if lightning had struck below the rim of the world. For a brief instant the mountains, and the land they encircled, were etched with fire against the darkness of the night. Ages later came the ghost of a far-off explosion, and in the woods below a sudden wind stirred among the trees. It died away swiftly, and one by one the routed stars crept back into the sky.

For the second time in his life, Alvin knew fear. It was not as personal and imminent as it had been in the chamber of the moving ways, when he had made the decision that took him to Lys. Perhaps it was awe rather than fear; he was looking into the face of the unknown, and it was as if he had already sensed that out there beyond the mountains was something he must go to meet.

"What was that?" he whispered at length.

There was a pause so long that he repeated the question.

"I am trying to find out," said Hilvar, and was silent again. Alvin guessed what he was doing and did not interrupt his friend's silent quest.

Presently Hilvar gave a little sigh of disappointment. "Everyone is asleep," he said. "There was no one who could tell me. We must wait until morning, unless I wake one of my friends. And I would not like to do that unless it is really important."

Alvin wondered what Hilvar would consider a matter of real importance. He was just going to suggest, a little sarcastically, that this might well merit interrupting someone's sleep. Before he could make the proposal, Hilvar spoke again.

"I've just remembered," he said, rather apologetically, "it's a long time since I came here, and I'm not quite certain about my bearings. But that must be Shalmirane."

"Shalmirane! Does it still exist?"

"Yes; I'd almost forgotten. Seranis once told me that the fortress lies in those mountains. Of course, its been in ruins for ages, but perhaps someone still lives there."

Shalmirane! To these children of two races, so widely differing in culture and history, this was indeed a name of magic. In all the long story of Earth, there had been no greater epic than the defense of Shalmirane against an invader who had conquered all the Universe. Though the true facts were utterly lost in the mists which had gathered so thickly around the Dawn Ages, the legends had never been forgotten and would last as long as man endured.

Presently Hilvar's voice came again out of the darkness.

"The people of the south could tell us more. I have some friends there; I will call them in the morning."

Alvin scarcely heard him; he was deep in his own thoughts, trying to remember all that he had ever heard of Shalmirane. It was little enough; after this immense lapse of time, no one could tell the truth from the legend. All that was certain was that the Battle of Shalmirane marked the end of Man's conquests and the beginning of his long decline.

Among those mountains, thought Alvin, might lie the answers to all the problems that had tormented him for so many years.

"How long," he said to Hilvar, "would it take us to reach the fortress?"

"I've never been there, but it's much farther than I intended to go. I doubt if we could do it in a day."

"Can't we use the ground-car?"

"No; the way lies through the mountains and no cars can go there."

Alvin thought it over. He was tired, his feet were sore, and the muscles of his thighs were still aching from the unaccustomed effort. It was very tempting to leave it for another time. Yet there might be no other time.

Beneath the dim light of the falling stars, not a few of which had died since Shalmirane was built, Alvin wrestled with his thoughts and presently made his decision. Nothing had changed; the mountains resumed their watch over the sleeping land. But a turning point in history had come and gone, and the human race was moving toward a strange new future.

Alvin and Hilvar slept no more that night, but broke camp with the first glow of dawn. The hill was drenched with dew, and Alvin marvelled at the sparkling jewellery which weighed down each blade and leaf. The "swish" of the wet grass fascinated him as he ploughed through it, and looking back up the hill he could see his path stretching behind him like a dark band across the shining ground.

The sun had just lifted above the eastern wall of Lys when they reached the outskirts of the forest. Here, Nature had returned to her own. Even Hilvar seemed somewhat lost among the gigantic trees that blocked the sunlight and cast pools of shadow on the jungle floor. Fortunately the river from the falls flowed south in a line too straight to be altogether natural and by keeping to its edge they could avoid the denser undergrowth. A good deal of Hilvar's time was spent in controlling Krif, who disappeared occasionally into the jungle or went skimming wildly across the water. Even Alvin, to whom everything was still so new, could feel that the forest had a fascination not possessed by the smaller, more cultivated woods of northern Lys. Few trees were alike; most of them were in various stages of devolution and some had reverted through the ages almost to their original, natural forms. Many were obviously not of Earth at all---probably not even of the Solar System. Watching like sentinels over the lesser trees were giant sequoias, three or four hundred feet high. Once they had been called the oldest things on Earth; they were still a little older than Man.

The river was widening now; ever and again it opened into small lakes, upon which tiny islands lay at anchor. There were insects here, brilliantly coloured creatures swinging to and fro over the surface of the water. Once, despite Hilvar's commands, Krif darted away to join his distant cousins. He disappeared instantly in a cloud of glittering wings, and the sound of angry buzzing floated toward them. A moment later the cloud erupted and Krif came back across the water, almost too quickly for the eye to follow. Thereafter he kept very close to Hilvar and did not stray again.

Toward evening they caught occasional glimpses of the mountains ahead. The river that had been so faithful a guide was flowing sluggishly now, as if it too were nearing the end of its journey. But it was clear that they could not reach the mountains by nightfall; well before sunset the forest had become so dark that further progress was impossible. The great trees lay in pools of shadow, and a cold wind was sweeping through the leaves. Alvin and Hilvar settled down for the night beside a giant redwood whose topmost branches were still ablaze with sunlight.

When at last the hidden sun went down, the light still lingered on the dancing waters. The two explorers---for such they now considered themselves, and such indeed they were---lay in the gathering gloom, watching the river and thinking of all that they had seen. Presently Alvin felt once again steal over him that sense of delicious drowsiness he had known for the first time on the previous night, and he gladly resigned himself to sleep. It might not be needed in the effortless life of Diaspar, but he welcomed it here. In the final moment before unconsciousness overcame him, he found himself wondering who last had come this way, and how long since.

+++

The sun was high when they left the forest and stood at last before the mountain walks of Lys. Ahead of them the ground rose steeply to the sky in waves of barren rock. Here the river came to an end as spectacular as its beginning, for the ground opened in its path and it sank roaring from sight. Alvin wondered what happened to it, and through what subterranean caves it travelled before it emerged again into the light of day. Perhaps the lost oceans of Earth still existed, far down in the eternal darkness, and this ancient river still felt the call that drew it to the sea.

For a moment Hilvar stood looking at the whirlpool and the broken land beyond. Then he pointed to a gap in the hills.

"Shalmirane lies in that direction," he said confidently. Alvin did not ask how he knew; he assumed that Hilvar's mind had made brief contact with that of a friend many miles away, and the information he needed had been silently passed to him.

It did not take long to reach the gap, and when they had passed through it they found themselves facing a curious plateau with gently sloping sides. Alvin felt no tiredness now, and no fear---only a taut expectancy and a sense of approaching adventure. What he would discover, he had no conception. That he would discover something he did not doubt at all.

As they approached the summit, the nature of the ground altered abruptly. The lower slopes had consisted of porous, volcanic stone, piled here and there in great mounds of slag. Now the surface turned suddenly to hard, glassy sheets, smooth and treacherous, as if the rock had once run in molten rivers down the mountain.

The rim of the plateau was almost at their feet. Hilvar reached it first, and a few seconds later Alvin overtook him and stood speechless at his side. For they stood on the edge, not of the plateau they had expected, but of a giant bowl half a mile deep and three miles in diameter. Ahead of them the ground plunged steeply downward, slowly levelling out at the bottom of the valley and rising again, more and more steeply, to the opposite rim. The lowest part of the bowl was occupied by a circular lake, the surface of which trembled continually, as if agitated by incessant waves.

Although it lay in the full glare of the sun, the whole of that great depression was ebony black. What material formed the crater, Alvin and Hilvar could not even guess, but it was black as the rock of a world that had never known a sun. Nor was that all, for lying beneath their feet and ringing the entire crater was a seamless band of metal, some hundred feet wide, tarnished by immeasurable age but still showing no slightest sign of corrosion.

As their eyes grew accustomed to the unearthly scene, Alvin and Hilvar realized that the blackness of the bowl was not as absolute as they had thought. Here and there, so fugitive that they could only see them indirectly, tiny explosions of light were flickering in the ebony walls. They came at random, vanishing as soon as they were born, like the reflections of stars on a broken sea.

"It's wonderful!" gasped Alvin. "But what is it?"

"It looks like a reflector of some kind."

"But it's so black!"

"Only to our eyes, remember. We do not know what radiations they used."

"But surely there must be more than this! Where is the fortress?"

Hilvar pointed to the lake.

"Look carefully," he said.

Alvin stared through the quivering roof of the lake, trying to plumb the secrets it concealed within its depths. At first he could see nothing; then, in the shallows near its edge, he made out a faint reticulation of light and shade. He was able to trace the pattern out toward the centre of the lake until the deepening water hid all further details.

The dark lake had engulfed the fortress. Down there lay the ruins of once mighty buildings, overthrown by time. Yet not all of them had been submerged, for on the far side of the crater Alvin now noticed piles of jumbled stones, and great blocks that must once have formed part of massive walls. The waters lapped around them, but had not yet risen far enough to complete their victory.

"We'll go round the lake," said Hilvar, speaking softly as if the majestic desolation had struck awe into his soul. "Perhaps we may find something in those ruins over there."

For the first few hundred yards the crater walls were so steep and smooth that it was difficult to stand upright, but after a while they reached the gentler slopes and could walk without difficulty. Near the border of the lake the smooth ebony of the surface was concealed by a thin layer of soil, which the winds of Lys must have brought here through the ages.

A quarter of a mile away, titanic blocks of stone were piled one upon the other, like the discarded toys of an infant giant. Here, a section of a massive wall was still recognizable; there, two carven obelisks marked what had once been a mighty entrance. Everywhere grew mosses and creeping plants, and tiny stunted trees. Even the wind was hushed.

So Alvin and Hilvar came to the ruins of Shalmirane. Against those walls, and against the energies they had housed, forces that could shatter a world to dust had flamed and thundered and been utterly defeated. Once these peaceful skies had blazed with fires torn from the hearts of suns, and the mountains of Lys must have quailed like living things beneath the fury of their masters.

No one had ever captured Shalmirane. But now the fortress, the impregnable fortress, had fallen at last---captured and destroyed by the patient tendrils of the ivy, the generations of blindly burrowing worms, and the slowly rising waters of the lake.

Overawed by its majesty, Alvin and Hilvar walked in silence toward the colossal wreck. They passed into the shadow of a broken wall, and entered a canyon where the mountains of stone had split asunder. Before them lay the lake, and presently they stood with the dark water lapping at their feet. Tiny waves, no more than a few inches high, broke endlessly upon the narrow shore.

Hilvar was the first to speak, and his voice held a hint of uncertainty which made Alvin glance at him in sudden surprise.

"There's something here I don't understand," he said slowly. "There's no wind, so what causes these ripples? The water should be perfectly still."

Before Alvin could think of any reply, Hilvar dropped to the ground, turned his head on one side, and immersed his right ear in the water. Alvin wondered what he hoped to discover in such a ludicrous position; then he realized that he was listening. With some repugnance---for the rayless waters looked singularly uninviting---he followed Hilvar's example.

The first shock of coldness lasted only for a second; when it passed he could hear, faint but distinct, a steady, rhythmic throbbing. It was as if he could hear, from far down in the depths of the lake, the beating of a giant heart.

They shook the water from their hair and stared at each other with silent surmise. Neither liked to say what he thought---that the lake was alive.

"It would be best," said Hilvar presently, "if we searched among these ruins and kept away from the lake."

"Do you think there's something down there?" asked Alvin, pointing to the enigmatic ripples that were still breaking against his feet. "Could it be dangerous?"

"Nothing that possesses a mind is dangerous," Hilvar replied. (Is that true? thought Alvin. What of the Invaders?) "I can detect no thoughts of any kind here, but I do not believe we are alone. It is very strange."

They walked slowly back toward the ruins of the fortress, each carrying in his mind the sound of that steady, muffled pulsing. It seemed to Alvin that mystery was piling upon mystery, and that for all his efforts he was getting further and further from any understanding of the truths he sought.

It did not seem that the ruins could teach them anything, but they searched carefully among the piles of rubble and the great mounds of stone. Here, perhaps, lay the graves of buried machines---the machines that had done their work so long ago. They would be useless now, thought Alvin, if the Invaders returned. Why had they never come back? But that was yet another mystery: he had enough enigmas to deal with--there was no need to seek any more.

A few yards from the lake they found a small clearing among the rubble. It had been covered with weeds, but they were now blackened and charred by tremendous heat, so that they crumbled to ashes as Alvin and Hilvar approached, smearing their legs with streaks of charcoal. At the centre of the clearing stood a metal tripod, firmly anchored to the ground, and supporting a circular ring which was tilted on its axis so that it pointed to a spot halfway up the sky. At first sight it seemed that the ring enclosed nothing; then, as Alvin looked more carefully, he saw that it was filled with a faint haze that tormented the eye by lurking at the edge of the visible spectrum. It was the glow of power, and from this mechanism, he did not doubt, had come the explosion of light that had lured them to Shalmirane.

They did not venture any closer, but stood looking at the machine from a safe distance. They were on the right track, thought Alvin; now it only remained to discover who, or what, had set this apparatus here, and what their purpose might be. That tilted ring---it was clearly aimed out into space. Had the flash they had observed been some kind of signal? That was a thought which had breath-taking implications.

"Alvin," said Hilvar suddenly, his voice quiet but urgent, "we have visitors."

Alvin spun on his heels and found himself staring at a triangle of lidless eyes. That, at least, was his first impression, then behind the staring eyes he saw the outlines of a small but complex machine. It was hanging in the air a few feet above the ground, and it was like no robot he had ever before seen.

Once the initial surprise had worn off, he felt himself the complete master of the situation. All his life he had given orders to machines, and the fact that this one was unfamiliar was of no importance. For that matter, he had never seen more than a few per cent of the robots that provided his daily needs in Diaspar.

"Can you speak?" he asked.

There was silence.

"Is anyone controlling you?"

Still silence.

"Go away. Come here. Rise. Fall."

None of the conventional control thoughts produced any effect. The machine remained contemptuously inactive. That suggested two possibilities. It was either too unintelligent to understand him or it was very intelligent indeed, with its own powers of choice and volition. In that case, he must treat it as an equal. Even then he might underestimate it, but it would bear him no resentment, for conceit was not a vice from which robots often suffered.

Hilvar could not help laughing at Alvin's obvious discomfiture. He was just about to suggest that he should take over the task of communicating, when the words died on his lips. The stillness of Shalmirane was shattered by an ominous and utterly unmistakable sound---the gurgling splash of a very large body emerging from water.

It was the second time since he had left Diaspar that Alvin wished he were at home. Then he remembered that this was not the spirit in which to meet adventure, and he began to walk slowly but deliberately toward the lake.

The creature now emerging from the dark water seemed a monstrous parody, in living matter, of the robot that was still subjecting them to its silent scrutiny. That same equilateral arrangement of eyes could be no coincidence; even the pattern of tentacles and little jointed limbs had been roughly reproduced. Beyond that, however, the resemblance ceased. The robot did not possess---it obviously did not require---the fringe of delicate, feathery palps which beat the water with a steady rhythm, the stubby multiple legs on which the beast was humping itself ashore, or the ventilating inlets, if that was what they were, which now wheezed fitfully in the thin air.

Most of the creature's body remained in the water; only the first ten feet reared itself into what was clearly an alien element. The entire beast was about fifty feet long, and even anyone with no knowledge of biology would have realized that there was something altogether wrong about it. It had an extraordinary air of improvisation and careless design, as if its components had been manufactured without much forethought and thrown roughly together when the need arose.

Despite its size and their initial doubts, neither Alvin nor Hilvar felt the slightest nervousness once they had had a clear look at the dweller in the lake. There was an engaging clumsiness about the creature which made it quite impossible to regard it as a serious menace, even if there was any reason to suppose it might be dangerous. The human race had long ago overcome its childhood terror of the merely alien in appearance. That was a fear which could no longer survive after the first contact with friendly extraterrestrial races.

"Let me deal with this," said Hilvar quietly. "I'm used to handling animals."

"But this isn't an animal," whispered Alvin in return. "I'm sure it's intelligent, and owns that robot."

"The robot may own it. In any case, its mentality must be very strange. I can still detect no sign of thought. Hello---what's happening?"

The monster had not moved from its half-raised position at the water's edge, which it seemed to be maintaining with considerable effort. But a semitransparent membrane had begun to form at the center of the triangle of eyes—a membrane that pulsed and quivered and presently started to emit audible sounds. They were low-pitched, resonant boomings which created no intelligible words, though it was obvious that the creature was trying to speak to them.

It was painful to watch this desperate attempt at communication. For several minutes the creature struggled in vain; then, quite suddenly, it seemed to realize that it had made a mistake. The throbbing membrane contracted in size, and the sounds it emitted rose several octaves in frequency until they entered the spectrum of normal speech. Recognizable words began to form, though they were still interspersed with gibberish. It was as if the creature was remembering a vocabulary it had known long ago but had had no occasion to use for many years.

Hilvar tried to give what assistance he could.

"We can understand you now," he said, speaking slowly and distinctly. "Can we help you? We saw the light you made. It brought us here from Lys."

At the word "Lys" the creature seemed to droop as if it had suffered some bitter disappointment.

"Lys," it repeated; it could not manage the "s" very well, so that the word sounded like "Lyd." "Always from Lys. No one else ever comes. We call the Great Ones, but they do not hear."

"Who are the Great Ones?" asked Alvin, leaning forward eagerly. The delicate, ever-moving palps waved briefly toward the sky.

"The Great Ones," it said. "From the planets of eternal day. They will come. The Master promised us."

This did not seem to make matters any clearer. Before Alvin could continue his cross-examination, Hilvar intervened again. His questioning was so patient, so sympathetic, and yet so penetrating that Alvin knew better than to interrupt, despite his eagerness. He did not like to admit that Hilvar was his superior in intelligence, but there was no doubt that his flair for handling animals extended even to this fantastic being. What was more, it seemed to respond to him. Its speech became more distinct as the conversation proceeded, and where at first it had been brusque to the point of rudeness, it presently elaborated its answers and volunteered information on its own.

Alvin lost all consciousness of the passage of time as Hilvar pieced together the incredible story. They could not discover the whole truth; there was endless room for conjecture and debate. As the creature answered Hilvar's questions ever more and more willingly, its appearance began to change. It slumped back into the lake, and the stubby legs that had been supporting it seemed to dissolve into the rest of its body. Presently a still more extraordinary change occurred; the three huge eyes slowly closed, shrank to pinpoints, and vanished completely. It was as if the creature had seen all that it wished to for the moment, and therefore had no further use for eyes.

Other and more subtle alterations were continually taking place, and eventually almost all that remained above the surface of the water was the vibrating diaphragm through which the creature spoke. Doubtless this too would be dissolved back into the original amorphous mass of protoplasm when it was no longer required.

Alvin found it hard to believe that intelligence could reside in so unstable a form---and his biggest surprise was yet to come. Though it seemed obvious that the creature was not of terrestrial origin, it was some time before even Hilvar, despite his greater knowledge of biology, realized the type of organism they were dealing with. It was not a single entity; in all their conversations with it, it always referred to itself as "we." In fact, it was nothing less than a colony of independent creatures, organized and controlled by unknown forces.

Animals of a remotely similar type---the medusae, for example---had once flourished in the ancient oceans of Earth. Some of them had been of great size, trailing their translucent bodies and forests of stinging tentacles over fifty or a hundred feet of water. But none of them had attained even the faintest flicker of intelligence, beyond the power to react to simple stimuli.

There was certainly intelligence here, though it was a failing, degenerating intelligence. Never was Alvin to forget this unearthly meeting, as Hilvar slowly pieced together the story of the Master, while the protean polyp groped for unfamiliar words, the dark lake lapped at the ruins of Shalmirane, and the trioptic robot watched them with unwavering eyes.

TRY as she would, Alystra could extract no further information from Khedron. The Jester had recovered quickly from his initial shock, and from the panic that had sent him flying back to the surface when he found himself alone in the depths beneath the Tomb. He also felt ashamed of his cowardly behaviour, and wondered if he would ever have the courage to return to the chamber of the moving ways and the network of world-ranging tunnels that radiated from it. Although he felt that Alvin had been impatient, if not indeed foolhardy, he did not really believe that he would run into any danger. He would return in his own good time. Khedron was certain of that. Well, almost certain; there was just enough doubt to make him feel the need for caution. It would be wise, he decided, to say as little as possible for the time being, and to pass the whole thing off as another joke.

Unfortunately for this plan, he had not been able to mask his emotions when Alystra encountered him on his return to the surface. She had seen the fear written so unmistakably in his eyes, and had at once interpreted it as meaning that Alvin was in danger. All Khedron's reassurances were in vain, and she became more and more angry with him as they walked together back through the park. At first Alystra had wanted to remain at the Tomb, waiting for Alvin to return in whatever mysterious manner he had vanished. Khedron had managed to convince her that this would be a waste of time, and was relieved when she followed him back to the city. There was a chance that Alvin might return almost at once, and he did not wish anyone else to discover the secret of Yarlan Zey.

By the time they had reached the city, it was obvious to Khedron that his evasive tactics had failed completely and that the situation was seriously out of hand. It was the first time in his life that he had ever been at a loss and had not felt himself capable of dealing with any problem that arose. His immediate and irrational fear was being slowly replaced by a profounder and more firmly based alarm. Until now, Khedron had given little thought to the consequences of his actions. His own interests, and a mild but genuine empathy toward Alvin, had been sufficient motive for all that he had done. Though he had given encouragement and assistance to Alvin, he had never believed that anything like this could ever really happen.

Despite the gulf of years and experience between them, Alvin's will had always been more powerful than his own. It was too late to do anything about it now; Khedron felt that events were sweeping him along toward a climax utterly beyond his control.

In view of this, it was a little unfair that Alystra obviously regarded him as Alvin's evil genius and showed an inclination to blame him for all that had happened. Alystra was not really vindictive, but she was annoyed, and part of her annoyance focused on Khedron. If any action of hers caused him trouble, she would be the last person to be sorry.

They parted in stony silence when they had reached the great circular way that surrounded the park. Khedron watched Alystra disappear into the distance and wondered wearily what plans were brewing in her mind.

There was only one thing of which he could be certain now. Boredom would not be a serious problem for a considerable time to come.

Alystra acted swiftly and with intelligence. She did not bother to contact Eriston and Etania; Alvin's parents were pleasant nonentities for whom she felt some affection but no respect. They would only waste time in futile arguments and would then do exactly as Alystra was doing now.

Jeserac listened to her story without apparent emotion. If he was alarmed or surprised, he concealed it well---so well that Alystra was somewhat disappointed. It seemed to her that nothing so extraordinary and important as this had ever happened before, and Jeserac's matter-of-fact behaviour made her feel deflated. When she had finished, he questioned her at some length, and hinted, without actually saying so, that she might have made a mistake. What reason was there for supposing that Alvin had really left the city? Perhaps it had been a trick at her expense; the fact that Khedron was involved made this seem highly probable. Alvin might be laughing at her, concealed somewhere in Diaspar, at this very moment.

The only positive reaction she got out of Jeserac was a promise to make inquiries and to contact her again within a day. In the meantime she was not to worry, and it would also be best if she said nothing to anyone else about the whole affair. There was no need to spread alarm over an incident that would probably be cleared up in a few hours.

Alystra left Jeserac in a mood of mild frustration. She would have been more satisfied could she have seen his behaviour immediately after she had left.

Jeserac had friends on the Council; he had been a member himself in his long life, and might be again if he was unlucky. He called three of his most influential colleagues and cautiously aroused their interest. As Alvin's tutor, he was well aware of his own delicate position and was anxious to safeguard himself. For the present, the fewer who knew what had happened, the better.

It was immediately agreed that the first thing to do was to contact Khedron and ask him for an explanation. There was only one defect in the excellent plan. Khedron had anticipated it and was nowhere to be found.

+++

If there was any ambiguity about Alvin's position, his hosts were very careful not to remind him of it. He was free to go anywhere he wished in Airlee, the little village over which Seranis ruled---though that was too strong a word to describe her position. Sometimes it seemed to Alvin that she was a benevolent dictator, but at others it appeared that she had no powers at all. So far he had failed completely to understand the social system of Lys, either because it was too simple or else so complex that its ramifications eluded him. All he had discovered for certain was that Lys was divided into innumerable villages, of which Airlee was a quite typical example. Yet in a sense there were no typical examples, for Alvin had been assured that every village tried to be as unlike its neighbours as possible. It was all extremely confusing.

Though it was very small, and contained less than a thousand people, Airlee was full of surprises. There was hardly a single aspect of life that did not differ from its counterpart in Diaspar. The differences extended even to such fundamentals as speech. Only the children used their voices for normal communication; the adults scarcely ever spoke, and after a while Alvin decided that they did so only out of politeness to him. It was a curiously frustrating experience to feel oneself enmeshed in a great net of soundless and undetectable words, but after a while Alvin grew accustomed to it. It seemed surprising that vocal speech had survived at all since there was no longer any use for it, but Alvin later discovered that the people of Lys were very fond of singing, and indeed of all forms of music. Without this incentive, it was very likely that they would long ago have become completely mute.

They were always busy, engaged in tasks or problems which were usually incomprehensible to Alvin. When he could understand what they were doing, much of their work seemed quite unnecessary. A considerable part of their food, for example, was actually grown, and not synthesized in accordance with patterns worked out ages ago. When Alvin commented on this, it was patiently explained to him that the people of Lys liked to watch things grow, to carry out complicated genetic experiments and to evolve ever more subtle tastes and flavours. Airlee was famous for its fruits, but when Alvin ate some choice samples they seemed to him no better than those he could have conjured up in Diaspar by no more effort than raising a finger.

At first he wondered if the people of Lys had forgotten, or had never possessed, the powers and machines that he took for granted and upon which all life in Diaspar was based. He soon found that this was not the case. The tools and the knowledge were there, but they were used only when it was essential. The most striking example of this was provided by the transport system, if it could be dignified by such a name. For short distances, people walked, and seemed to enjoy it. If they were in a hurry, or had small loads to move, they used animals which had obviously been developed for the purpose. The freight-carrying species was a low, six-legged beast, very docile and strong but of poor intelligence. The racing animals were of a different breed altogether, normally walking on four legs but using only their heavily muscled hind limbs when they really got up speed. They could cross the entire width of Lys in a few hours, and the passenger rode in a pivoted seat strapped on the creature's back. Nothing in the world would have induced Alvin to risk such a ride, though it was a very popular sport among the younger men. Their finely bred steeds were the aristocrats of the animal world, and were well aware of it. They had fairly large vocabularies, and Alvin often overheard them talking boastfully among themselves about past and future victories. When he tried to be friendly and attempted to join in the conversation, they pretended that they could not understand him, and if he persisted would go bounding off in outraged dignity.

These two varieties of animal sufficed for all ordinary needs, and gave their owners a great deal of pleasure which no mechanical contrivances could have done. But when extreme speed was required or vast loads had to be moved, the machines were there, and were used without hesitation.

Though the animal life of Lys presented Alvin with a whole world of new interests and surprises, it was the two extremes of the human population range that fascinated him most of all. The very young and the very old---both were equally strange to him and equally amazing. Airlee's most senior inhabitant had barely attained his second century, and had only a few more years of life before him. When he had reached that age, Alvin reminded himself, his body would scarcely have altered, whereas this old man, who had no chain of future existences to look forward to as compensation, had almost exhausted his physical powers. His hair was completely white, and his face an unbelievably intricate mass of wrinkles. He seemed to spend most of his time sitting in the sun or walking slowly around the village exchanging soundless greetings with everyone he met. As far as Alvin could tell he was completely contented, asking no more of life, and was not distressed by its approaching end.

Here was a philosophy so much at variance with that of Diaspar as to be completely beyond Alvin's comprehension. Why should anyone accept death when it was so unnecessary, when you had the choice of living for a thousand years and then leaping forward through the millenniums to make a new start in a world that you had helped to shape? This was one mystery he was determined to solve as soon as he had the chance of discussing it frankly. It was very hard for him to believe that Lys had made this choice of its own free will, if it knew the alternative that existed.

He found part of his answer among the children, those little creatures who were as strange to him as any of the animals of Lys. He spent much of his time among them, watching them at their play and eventually being accepted by them as a friend. Sometimes it seemed to him that they were not human at all, their motives, their logic, and even their language were so alien. He would look unbelievingly at the adults and ask himself how it was possible that they could have evolved from these extraordinary creatures who seemed to spend most of their lives in a private world of their own.

And yet, even while they baffled him, they aroused within his heart a feeling he had never known before. When---which was not often, but sometimes happened---they burst into tears of utter frustration or despair, their tiny disappointments seemed to him more tragic than Man's long retreat after the loss of his Galactic Empire. That was something too huge and remote for comprehension, but the weeping of a child could pierce one to the heart.

Alvin had met love in Diaspar, but now he was learning something equally precious, and without which love itself could never reach its highest fulfillment but must remain forever incomplete. He was learning tenderness.

+++

If Alvin was studying Lys, Lys was also studying him, and was not dissatisfied with what it had found. He had been in Airlee for three days when Seranis suggested that he might like to go further afield and see something more of her country. It was a proposal he accepted at once---on condition that he was not expected to ride one of the village's prize racing beasts.

"I can assure you," said Seranis, with a rare flash of humour, "that no one here would dream of risking one of their precious animals. Since this is an exceptional case, I will arrange transport in which you will feel more at home. Hilvar will act as your guide, but of course you can go wherever you please."

Alvin wondered if that was strictly true. He imagined that there would be some objection if he tried to return to the little hill from whose summit he had first emerged into Lys. However, that did not worry him for the moment since he was in no hurry to go back to Diaspar, and indeed had given little thought to the problem after his initial meeting with Seranis. Life here was still so interesting and so novel that he was still quite content to live in the present.

He appreciated Seranis's gesture in offering her son as his guide, though doubtless Hilvar had been given careful instructions to see that he did not get into mischief. It had taken Alvin some time to get accustomed to Hilvar, for a reason which he could not very well explain to him without hurting his feelings. Physical perfection was so universal in Diaspar that personal beauty had been completely devalued; men noticed it no more than the air they breathed. This was not the case in Lys, and the most flattering adjective that could be applied to Hilvar was "homely". By Alvin's standards, he was downright ugly, and for a while he had deliberately avoided him. If Hilvar was aware of this, he showed no sign of it, and it was not long before his good-natured friendliness had broken through the barrier between them. The time was to come when Alvin would be so accustomed to Hilvar's broad, twisted smile, his strength, and his gentleness that he could scarcely believe he had ever found him unattractive, and would not have had him changed for any consideration in the world.

They left Airlee soon after dawn in a small vehicle which Hilvar called a ground-car, and which apparently worked on the same principle as the machine that had brought Alvin from Diaspar. It floated in the air a few inches above the turf, and although there was no sign of any guide rail, Hilvar told him that the cars could run only on predetermined routes. All the centres of population were linked together in this fashion, but during his entire stay in Lys Alvin never saw another ground-car in use.

Hilvar had put a great deal of effort into organizing this expedition, and was obviously looking forward to it quite as much as Alvin. He had planned the route with his own interests in mind, for natural history was his consuming passion and he hoped to find new types of insect life in the relatively uninhabited regions of Lys which they would be visiting. He intended to travel as far south as the machine could take them, and the rest of the way they would have to go on foot. Not realizing the full implications of this, Alvin made no objections.

They had a companion with them on the journey---Krif, the most spectacular of Hilvar's many pets. When Krif was resting, his six gauzy wings lay folded along his body, which glittered through them like a jewelled sceptre. If something disturbed him, he would rise into the air with a flicker of iridescence and a faint whirring of invisible wings. Though the great insect would come when called and would---sometimes---obey simple orders, it was almost wholly mindless. Yet it had a definite personality of its own, and for some reason was suspicious of Alvin, whose sporadic attempts to gain its confidence always ended in failure.

To Alvin, the journey across Lys had a dreamlike unreality. Silent as a ghost, the machine slid across rolling plains and wound its way through forests, never deviating from its invisible track. It travelled perhaps ten times as fast as a man could comfortably walk; seldom indeed was any inhabitant of Lys in a greater hurry than that.

They passed through many villages, some larger than Airlee but most of them built along very similar lines. Alvin was interested to notice the subtle but significant differences in clothing and even physical appearance that occurred as they moved from one community to the next. The civilization of Lys was composed of hundreds of distinct cultures, each contributing some special talent toward the whole. The ground-car was well stocked with Airlee's most famous product, a small, yellow peach which was gratefully received whenever Hilvar gave away some samples. He often stopped to talk to friends and to introduce Alvin, who never ceased to be impressed by the simple courtesy with which everyone used vocal speech as soon as they knew who he was. It must often have been very tedious to them, but as far as he could judge they always resisted the temptation to lapse into telepathy and he never felt excluded from their conversation.

They made their longest pause at a tiny village almost hidden in a sea of tall golden grass, which soared high above their heads and which undulated in the gentle wind as if it was endowed with life. As they moved through it, they were continually overtaken by rolling waves as the countless blades bowed in unison above them. At first it was faintly disturbing, for Alvin had a foolish fancy that the grass was bending down to look at him, but after a while he found the continual motion quite restful.

Alvin soon discovered why they had made this stop. Among the little crowd that had already gathered before the car came gliding into the village was a shy, dark girl whom Hilvar introduced as Nyara. They were obviously very pleased to see one another again, and Alvin felt envious of their patent happiness at this brief reunion. Hilvar was clearly torn between his duties as a guide and his desire to have no other company but Nyara, and Alvin soon rescued him from his quandary by setting off on a tour of exploration by himself. There was not much to see in the little village, but he took his time.

When they started on their way again, there were many questions he was anxious to ask Hilvar. He could not imagine what love must be like in a telepathic society, and after a discreet interval he broached the subject. Hilvar was willing enough to explain, even though Alvin suspected that he had made his friend interrupt a prolonged and tender mental leave-taking.

In Lys, it seemed, all love began with mental contact, and it might be months or years before a couple actually met. In this way, Hilvar explained, there could be no false impressions, no deceptions on either side. Two people whose minds were open to one another could hide no secrets. If either attempted it, the other partner would know at once that something was being concealed.

Only very mature and well-balanced minds could afford such honesty; only love based upon absolute unselfishness could survive it. Alvin could well understand that such a love would be deeper and richer than anything his people could know; it could be so perfect, in fact, that he found it hard to believe that it could ever occur at all.

Yet Hilvar assured him that it did, and became starry-eyed and lost in his own reveries when Alvin pressed him to be more explicit. There were some things that could not be communicated; one either knew them or one did not. Alvin decided sadly that he could never attain the kind of mutual understanding which these fortunate people had made the very basis of their lives.

When the ground-car emerged from the savanna, which ended abruptly as though a frontier had been drawn beyond which the grass was not permitted to grow, there was a range of low, heavily wooded hills ahead of them. This was an outpost, Hilvar explained, of the main rampart guarding Lys. The real mountains lay beyond, but to Alvin even these small hills were an impressive and awe-inspiring sight.

The car came to a halt in a narrow, sheltered valley which was still flooded by the warmth and light of the descending sun. Hilvar looked at Alvin with a kind of wide-eyed candour which, one could have sworn, was totally innocent of any guile.

"This is where we start to walk," he said cheerfully, beginning to throw equipment out of the vehicle. "We can't ride any farther."

Alvin looked at the hills surrounding them, then at the comfortable seat in which he had been riding.

"Isn't there a way around?" he asked, not very hopefully.

"Of course," replied Hilvar. "But we're not going around. We're going to the top, which is much more interesting. I'll put the car on automatic so that it will be waiting for us when we get down the other side."

Determined not to give in without a struggle, Alvin made one last effort.

"It will soon be dark," he protested. "We'll never be able to go all that way before sunset."

"Exactly," said Hilvar, sorting packages and equipment with incredible speed. "We'll spend the night on the summit, and finish the journey in the morning."

For once, Alvin knew when he was beaten.

The gear that they were carrying looked very formidable, but though it was bulky it weighed practically nothing. It was all packed in gravity-polarizing containers that neutralized its weight, leaving only inertia to be contended with. As long as Alvin moved in a straight line, he was not conscious that he was carrying any load. Dealing with these containers required a little practice, for if he attempted to make a sudden change of direction his pack seemed to develop a stubborn personality and did its best to keep him on his original course, until he had overcome its momentum.

When Hilvar had adjusted all the straps and satisfied himself that everything was in order, they began to walk slowly up the valley. Alvin looked back wistfully as the ground-car retraced its track and disappeared from sight; he wondered how many hours would elapse before he could again relax in its comfort.

Nevertheless, it was very pleasant climbing upward with the mild sun beating on their backs, and seeing ever-new vistas unfold around them. There was a partly obliterated path which disappeared from time to time but which Hilvar seemed able to follow even when Alvin could see no trace of it. He asked Hilvar what had made the path, and was told that there were many small animals in these hills---some solitary, and some living in primitive communities which echoed many of the features of human civilization. A few had even discovered, or been taught, the use of tools and fire. It never occurred to Alvin that such creatures might be other than friendly; both he and Hilvar took this for granted, for it had been so many ages since anything on Earth had challenged the supremacy of Man.

They had been climbing for half an hour when Alvin first noticed the faint, reverberating murmur in the air around him. He could not detect its source, for it seemed to come from no particular direction. It never ceased, and it grew steadily louder as the landscape widened around them. He would have asked Hilvar what it was, but it had become necessary to save his breath for more essential purposes.

Alvin was in perfect health; indeed, he had never had an hour's illness in his life. But physical well-being, however important and necessary it might be, was not sufficient for the task he was facing now. He had the body, but he did not possess the skill. Hilvar s easy strides, the effortless surge of power which took him up every slope, filled Alvin with envy---and a determination not to give in while he could still place one foot in front of the other. He knew perfectly well that Hilvar was testing him, and did not resent the fact. It was a good-natured game, and he entered into the spirit of it even while the fatigue spread slowly through his legs.

Hilvar took pity on him when they had completed two-thirds of the ascent, and they rested for a while propped up against a westward-facing bank, letting the mellow sunlight drench their bodies. The throbbing thunder was very strong now, and although Alvin questioned him Hilvar refused to explain it. It would, he said, spoil the surprise if Alvin knew what to expect at the end of the climb.

They were now racing against the sun, but fortunately the final ascent was smooth and gentle. The trees that had covered the lower part of the hill had now thinned out, as if they too were tired of the fight against gravity, and for the last few hundred yards the ground was carpeted with short, wiry grass on which it was very pleasant to walk. As the summit came in sight, Hilvar put forth a sudden burst of energy and went racing up the slope. Alvin decided to ignore the challenge; indeed, he had no choice. He was quite content to plod steadily onward, and when he had caught up with Hilvar to collapse in contented exhaustion by his side.

Not until he had regained his breath was he able to appreciate the view spread out beneath him, and to see the origin of the endless thunder which now filled the air. The ground ahead fell away steeply from the crest of the hill---so steeply, indeed, that it soon became an almost vertical cliff. And leaping far out from the face of the cliff was a mighty ribbon of water, which curved through space to crash into the rocks a thousand feet below. There it was lost in a shimmering mist of spray, while up from the depths rose that ceaseless, drumming thunder that reverberated in hollow echoes from the hills on either side.

Most of the waterfall was now in shadow, but the sunlight streaming past the mountain still illuminated the land beneath, adding the final touch of magic to the scene. For quivering in evanescent beauty above the base of the fall was the last rainbow left on Earth.

Hilvar waved his arm in a sweep which embraced the whole horizon.

"From here," he said, raising his voice so that it could be heard above the thunder of the waterfall, "you can see right across Lys."

Alvin could well believe him. To the north lay mile upon mile of forest, broken here and there by clearings and fields and the wandering threads of a hundred rivers. Hidden somewhere in that vast panorama was the village of Airlee, but it was hopeless to try to find it. Alvin fancied that he could catch a glimpse of the lake past which the path led to the entrance into Lys, but decided that his eyes had tricked him. Still farther north, trees and clearings alike were lost in a mottled carpet of green, rucked here and there by lines of hills. And beyond that, at the very edge of vision, the mountains that hemmed Lys from the desert lay like a bank of distant clouds.

East and west the view was little different, but to the south the mountains seemed only a few miles away. Alvin could see them very clearly, and he realized that they were far higher than the little peak on which he was standing. They were separated from him by country that was much wilder than the land through which he had just passed. In some indefinable way it seemed deserted and empty, as if Man had not lived here for many, many years.

Hilvar answered Alvin's unspoken question.

"Once that part of Lys was inhabited," he said. "I don't know why it was abandoned, and perhaps one day we shall move into it again. Only the animals live there now."

Indeed, there was nowhere any sign of human life---none of the clearings or well-disciplined rivers that spoke of Man's presence. Only in one spot was there any indication that he had ever lived here, for many miles away a solitary white ruin jutted above the forest roof like a broken fang. Elsewhere, the jungle had returned to its own.

The sun was sinking below the western walls of Lys. For a breathless moment, the distant mountains seemed to burn with golden flames; then the land they guarded was swiftly drowned with shadow and the night had come.

"We should have done this before," said Hilvar, practical as ever, as he started to unload their equipment. "It'll be pitch dark in five minutes---and cold, too."

Curious pieces of apparatus began to cover the grass. A slim tripod extended a vertical rod carrying a pear-shaped bulge at its upper end. Hilvar raised this until the pear was just clear of their heads, and gave some mental signal which Alvin could not intercept. At once their little encampment was flooded with light, and the darkness retreated. The pear gave not only light but also heat, for Alvin could feel a gentle, caressing glow that seemed to sink into his very bones.

Carrying the tripod in one hand and his pack in the other, Hilvar walked down the slope while Alvin hurried behind, doing his best to keep in the circle of light. He finally pitched camp in a small depression a few hundred yards below the crest of the hill, and started to put the rest of his equipment into operation.

First came a large hemisphere of some rigid and almost invisible material which englobed them completely and protected them from the cool breeze which had now begun to blow up the face of the hill. The dome appeared to be generated by a small rectangular box which Hilvar placed on the ground and then ignored completely, even to the extent of burying it beneath the rest of his paraphernalia. Perhaps this also projected the comfortable, semitransparent couches on which Alvin was so glad to relax. It was the first time he had seen furniture materialized in Lys, where it seemed to him that the houses were terribly cluttered up with permanent artifacts which would be much better kept safely out of the way in Memory Banks.

The meal which Hilvar produced from yet another of his receptacles was also the first purely synthetic one that Alvin had eaten since reaching Lys. There was a steady blast of air, sucked through some orifice in the dome overhead, as the matter-converter seized its raw material and performed its everyday miracle. On the whole, Alvin was much happier with purely synthetic food. The way in which the other kind was prepared struck him as being appallingly unhygienic, and at least with the matter-converters you knew exactly what you were eating.

They settled down for their evening meal as the night deepened around them and the stars came out. When they had finished, it was completely dark beyond their circle of light, and at the edge of that circle Alvin could see dim shapes moving as the creatures of the forest crept out of their hiding places. From time to time he caught the glint of reflected light as pale eyes stared back at him, but whatever beasts were watching out there would come no closer, so he could see nothing more of them.

It was very peaceful, and Alvin felt utterly content. For a while they lay on their couches and talked about the things that they had seen, the mystery that enmeshed them both, and the many ways in which their two cultures differed. Hilvar was fascinated by the miracle of the Eternity Circuits which had put Diaspar beyond the reach of time, and Alvin found some of his questions very hard to answer.

"What I don't understand," said Hilvar, "is how the designers of Diaspar made certain that nothing would ever go wrong with the memory circuits. You tell me that the information defining the city, and all the people who live in it, is stored as patterns of electric charge inside crystals. Well, crystals will last forever---but what about all the circuits associated with them? Aren't there ever any failures of any kind?"

"I asked Khedron that same question, and he told me that the Memory Banks are virtually triplicated. Any one of the three banks can maintain the city, and if anything goes wrong with one of them, the other two automatically correct it. Only if the same failure occurred simultaneously in two of the banks would any permanent damage be done---and the chances of that are infinitesimal."

"And how is the relation maintained between the pattern stored in the memory units and the actual structure of the city? Between the plan, as it were, and the thing it describes?"

Alvin was now completely out of his depth. He knew that the answer involved technologies that relied on the manipulation of space itself---but how one could lock an atom rigidly in the position defined by data stored elsewhere was something he could not begin to explain.

On a sudden inspiration, he pointed to the invisible dome protecting them from the night.

"Tell me how this roof above our heads is created by that box you're sitting on," he answered, "and then I'll explain how the Eternity Circuits work."

Hilvar laughed.

"I suppose it's a fair comparison. You'd have to ask one of our field theory experts if you wanted to know that. I certainly couldn't tell you."

The reply made Alvin very thoughtful. So there were still men in Lys who understood how their machines worked; that was more than could be said of Diaspar.

Thus they talked and argued, until presently Hilvar said: "I'm tired. What about you---are you going to sleep?"

Alvin rubbed his still-weary limbs.

"I'd like to," he confessed, "but I'm not sure I can. It still seems a strange custom to me."

"It is a good deal more than a custom," smiled Hilvar. "I have been told that it was once a necessity to every human being. We still like to sleep at least once a day, even if only for a few hours. During that time the body refreshes itself, and the mind as well. Does no one in Diaspar ever sleep?"

"Only on very rare occasions," said Alvin. "Jeserac, my tutor, has done it once or twice, after he had made some exceptional mental effort. A well-designed body should have no need for such rest periods; we did away with them millions of years ago."

Even as he spoke these rather boastful words, his actions belied them. He felt a weariness such as he had never before known; it seemed to spread from his calves and thighs until it flowed through all his body. There was nothing unpleasant about the sensation---rather the reverse. Hilvar was watching him with an amused smile, and Alvin had enough faculties left to wonder if his companion was exercising any of his mental powers upon him. If so, he did not object in the least.

The light flooding down from the metal pear overhead sank to a faint glow, but the warmth it was radiating continued unabated. By the last flicker of light, Alvin's drowsy mind registered a curious fact which he would have to inquire about in the morning.

Hilvar had stripped off his clothes, and for the first time Alvin saw how much the two branches of the human race had diverged. Some of the changes were merely ones of emphasis or proportion, but others, such as the external genitals and the presence of teeth, nails, and definite body hair, were more fundamental. What puzzled him most of all, however, was the curious small hollow in the pit of Hilvar's stomach.

When, some days later, he suddenly remembered the subject, it took a good deal of explaining. By the time that Hilvar had made the functions of the navel quite clear, he had uttered many thousands of words and drawn half a dozen diagrams.

And both he and Alvin had made a great step forward in understanding the basis of each other's cultures.

WHEN the door closed behind him, Alvin slumped into the nearest seat. All strength seemed suddenly to have been drained from his legs: at last he knew, as he had never known before, that fear of the unknown that haunted all his fellow men. He felt himself trembling in every limb, and his sight became misty and uncertain. Could he have escaped from this speeding machine he would willingly have done so, even at the price of abandoning all his dreams.

It was not fear alone that overwhelmed him, but a sense of unutterable loneliness. All that he knew and loved was in Diaspar; even if he was going into no danger, he might never see his world again. He knew, as no man had known for ages, what it meant to leave one's home forever. In this moment of desolation, it seemed to him of no importance whether the path he was following led to peril or to safety; all that mattered to him now was that it led away from home.

The mood slowly passed; the dark shadows lifted from his mind. He began to pay attention to his surroundings, and to see what he could learn from the unbelievably ancient vehicle in which he was travelling. It did not strike Alvin as particularly strange or marvellous that this buried transport system should still function perfectly after such aeons of time. It was not preserved in the eternity circuits of the city's own monitors, but there must be similar circuits elsewhere guarding it from change or decay.

For the first time he noticed the indicator board that formed part of the forward wall. It carried a brief but reassuring message:

LYS 35 MINUTES

Even as he watched, the number changed to "34." That at least was useful information, though since he had no idea of the machine's speed it told him nothing about the length of the journey. The walls of the tunnel were one continual blur of grey, and the only sensation of movement was a very slight vibration he would never have noticed had he not looked for it.

Diaspar must be many miles away by now, and above him would be the desert with its shifting sand dunes. Perhaps at this very moment he was racing below the broken hills he had watched so often from the Tower of Loranne.

His imagination sped onward to Lys, as if impatient to arrive ahead of his body. What sort of a city would it be? No matter how hard he tried, he could only picture another and smaller version of Diaspar. He wondered if it still existed, then assured himself that not otherwise would this machine be carrying him swiftly through the Earth.

Suddenly there was a distinct change in the vibration underfoot. The vehicle was slowing down---there was no question of that. The time must have passed more swiftly than he had thought; somewhat surprised, Alvin glanced at the indicator: LYS 23 MINUTES

Feeling puzzled, and a little worried, he pressed his face against the side of the machine. His speed was still blurring the walls of the tunnel into a featureless grey, yet now from time to time he could catch a glimpse of markings that disappeared almost as quickly as they came. And at each disappearance, they seemed to remain in his field of vision for a little longer.

Then, without any warning, the walls of the tunnel were snatched away on either side. The machine was passing, still at a very great speed, through an enormous empty space, far larger even than the chamber of the moving ways.

Peering in wonder through the transparent walls, Alvin could glimpse beneath him an intricate network of guiding rods, rods that crossed and criss-crossed to disappear into a maze of tunnels on either side. A flood of bluish light poured down from the arched dome of the ceiling, and silhouetted against the glare he could just make out the frameworks of great machines. The light was so brilliant that it pained the eyes, and Alvin knew that this place had not been intended for man. A moment later, his vehicle flashed past row after row of cylinders, lying motionless above their guide rails. They were much larger than the one in which he was travelling, and Alvin guessed that they must have been used for transporting freight. Around them were grouped incomprehensible, many-jointed mechanisms, all silent and stilled.

Almost as quickly as it had appeared, the vast and lonely chamber vanished behind him. Its passing left a feeling of awe in Alvin's mind; for the first time he really understood the meaning of that great, darkened map below Diaspar. The world was more full of wonder than he had ever dreamed.

Alvin glanced again at the indicator. It had not changed; he had taken less than a minute to flash through the great cavern. The machine was accelerating again; though there was little sense of motion, the tunnel walls were flowing past on either side at a speed he could not even guess.

It seemed an age before that indefinable change of vibration occurred again. Now the indicator was reading:

LYS 1 MINUTE

That minute was the longest that Alvin had ever known. More and more slowly moved the machine; this was no mere slackening of its speed. It was coming at last to rest.

Smoothly and silently the long cylinder slid out of the tunnel into a cavern that might have been the twin of the one below Diaspar. For a moment Alvin was too excited to see anything clearly; the door had been open for a considerable time before he realized that he could leave the vehicle. As he hurried out of the machine, he caught a last glimpse of the indicator. Its wording had now changed and its message was infinitely reassuring:

DIASPAR 35 MINUTES

As he began to search for a way out of the chamber, Alvin found the first hint that he might be in a civilization different from his own. The way to the surface clearly lay through a low, wide tunnel at one end of the cavern---and leading up through the tunnel was a flight of steps. Such a thing was extremely rare in Diaspar; the architects of the city had built ramps or sloping corridors whenever there was a change of level. This was a survival from the days when most robots had moved on wheels, and so found steps an impassable barrier.

The stairway was very short, and ended against doors that opened automatically at Alvin's approach. He walked into a small room like that which had carried him down the shaft under the Tomb of Yarlan Zey, and was not surprised when a few minutes later the doors opened again to reveal a vaulted corridor rising slowly to an archway that framed a semicircle of sky. There had been no sensation of movement, but Alvin knew that he must have risen many hundreds of feet. He hurried forward up the slope to the sunlit opening, all fear forgotten in his eagerness to see what lay before him.

He was standing at the brow of a low hill, and for an instant it seemed as if he were once again in the central park of Diaspar. Yet if this were indeed a park, it was too enormous for his mind to grasp. The city he had expected to see was nowhere visible. As far as the eye could reach there was nothing but forest and grass-covered plains.

Then Alvin lifted his eyes to the horizon, and there above the trees, sweeping from right to left in a great arc that encircled the world, was a line of stone which would have dwarfed the mightiest giants of Diaspar. It was so far away that its details were blurred by sheer distance, but there was something about its outlines that Alvin found puzzling. Then his eyes became at last accustomed to the scale of that colossal landscape, and he knew that those far-off walls had not been built by man.

Time had not conquered everything; Earth still possessed mountains of which she could be proud.

For a long time Alvin stood at the mouth of the tunnel, slowly growing accustomed to the strange world in which he had found himself. He was half stunned by the impact of sheer size and space; that ring of misty mountains could have enclosed a dozen cities as large as Diaspar. Search as he might, however, Alvin could see no trace of human life. Yet the road that led down the hillside seemed well-kept; he could do no better than accept its guidance.

At the foot of the hill, the road disappeared between great trees that almost hid the sun. As Alvin walked into their shadow, a strange medley of scents and sounds greeted him. The rustle of the wind among the leaves he had known before, but underlying that were a thousand vague noises that conveyed nothing to his mind. Unknown odours assailed him, smells that had been lost even to the memory of his race. The warmth, the profusion of scent and colour, and the unseen presences of a million living things, smote him with almost physical violence.

He came upon the lake without any warning. The trees to the right suddenly ended, and before him was a great expanse of water, dotted with tiny islands. Never in his life had Alvin seen so much water; by comparison, the largest pools in Diaspar were scarcely more than puddles. He walked slowly down to the edge of the lake and cupped the warm water in his hands, letting it trickle through his fingers.

The great silver fish that suddenly forced its way through the underwater reeds was the first nonhuman creature that Alvin had ever seen. It should have been utterly strange to him, yet its shape teased his mind with a haunting familiarity. As it hung there in the pale green void, its fins a faint blur of motion, it seemed the very embodiment of power and speed. Here, incorporated in living flesh, were the graceful lines of the great ships that had once ruled the skies of Earth. Evolution and science had come to the same answers; and the work of Nature had lasted longer.

At last Alvin broke the lake's enchantment, and continued along the winding road. The forest closed around him once more, but only for a little while. Presently the road ended, in a great clearing half a mile wide and twice as long---and Alvin understood why he had seen no trace of man before.

The clearing was full of low, two-storied buildings, coloured in soft shades that rested the eye even in the full glare of the sun. Most were of clean, straightforward design, but several were built in a complex architectural style involving the use of fluted columns and gracefully fretted stone. In these buildings, which seemed of great age, the immeasurably ancient device of the pointed arch was used.

As he walked slowly toward the village, Alvin was still struggling to grasp his new surroundings. Nothing was familiar; even the air had changed, with its hint of throbbing, unknown life. And the tall, golden-haired people going among the buildings with such unconscious grace were obviously of a different stock from the men of Diaspar. They took no notice of Alvin, and that was strange, for his clothing was totally different from theirs. Since the temperature never changed in Diaspar, dress there was purely ornamental and often extremely elaborate. Here it seemed mainly functional, designed for use rather than display, and frequently consisted of a single sheet draped around the body.

It was not until Alvin was well inside the village that the people of Lys reacted to his presence, and then their response took a somewhat unexpected form. A group of five men emerged from one of the houses and began to walk purposefully toward him---almost as if, indeed, they had been expecting his arrival. Alvin felt a sudden, heady excitement, and the blood pounded in his veins. He thought of all the fateful meetings men must have had with other races on far-off worlds. Those he was meeting now were of his own species---but how had they diverged in the aeons that had sundered them from Diaspar?

The delegation came to a halt a few feet away from Alvin. Its leader smiled, holding out his hand in the ancient gesture of friendship.

"We thought it best to meet you here," he said. "Our home is very different from Diaspar, and the walk from the terminus gives visitors a chance to become---acclimatized."

Alvin accepted the outstretched hand, but for a moment was too surprised to reply. Now he understood why all the other villagers had ignored him so completely.

"You knew I was coming?" he said at length.

"Of course. We always know when the carriers start to move. Tell me---how did you discover the way? It has been such a long time since the last visit that we feared the secret had been lost."

The speaker was interrupted by one of his companions.

"I think we'd better restrain our curiosity, Gerane. Seranis is waiting."

The name "Seranis" was preceded by a word unfamiliar to Alvin, and he assumed that it was a title of some kind. He had no difficulty in understanding the others, and it never occurred to him that there was anything surprising about this. Diaspar and Lys shared the same linguistic heritage, and the ancient invention of sound recording had long ago frozen speech in an unbreakable mould.

Gerane gave a shrug of mock resignation. "Very well," he smiled. "Seranis has few privileges---I should not rob her of this one."

As they walked deeper into the village, Alvin studied the men around him. They appeared kindly and intelligent, but he was looking for ways in which they differed from a similar group in Diaspar. There were differences, but it was hard to define them. They were all somewhat taller than Alvin, and two of them showed the unmistakable marks of physical age. Their skins were very brown, and in all their movements they seemed to radiate a vigour and zest which Alvin found refreshing, though at the same time a little bewildering. He smiled as he remembered Khedron's prophecy that, if he ever reached Lys, he would find it exactly the same as Diaspar.

The people of the village now watched with frank curiosity as Alvin followed his guides; there was no longer any pretence that they took him for granted. Suddenly there were shrill, high-pitched shouts from the trees on the right, and a group of small, excited creatures burst out of the woods and crowded around Alvin. He stopped in utter amazement, unable to believe his eyes. Here was something that his world had lost so long ago that it lay in the realms of mythology. This was the way that life had once begun; these noisy, fascinating creatures were human children.

Alvin watched them with wondering disbelief---and with another sensation which tugged at his heart but which he could not yet identify. No other sight could have brought home to him so vividly his remoteness from the world he knew. Diaspar had paid, and paid in full, the price of immortality.

The party halted before the largest building Alvin had yet seen. It stood in the centre of the village and from a flagpole on its small circular tower a green pennant floated along the breeze.

All but Gerane dropped behind as he entered the building. Inside it was quiet and cool; sunlight filtering through the translucent walls lit up everything with a soft, restful glow. The floor was smooth and resilient, inlaid with fine mosaics. On the walls, an artist of great ability and power had depicted a set of forest scenes. Mingled with these paintings were other murals which conveyed nothing to Alvin's mind, yet which were attractive and pleasant to look upon. Let into one wall was a rectangular screen filled with a shifting maze of colours---presumably a visophone receiver, though a rather small one.

They walked together up a short circular stairway that led them out onto the flat roof of the building. From this point, the entire village was visible, and Alvin could see that it consisted of about a hundred buildings. In the distance the trees opened out to enclose wide meadows, where animals of several different types were grazing. Alvin could not imagine what these were, most of them were quadrupeds, but some seemed to have six or even eight legs.

Seranis was waiting for him in the shadow of the tower. Alvin wondered how old she was; her long, golden hair was touched with grey, which he guessed must be some indication of age. The presence of children, with all the consequences that implied, had left him very confused. Where there was birth, then surely there must also be death, and the life span here in Lys might be very different from that in Diaspar. He could not tell whether Seranis was fifty, five hundred, or five thousand years old, but looking into her eyes he could sense that wisdom and depth of experience he sometimes felt when he was with Jeserac.

She pointed to a small seat, but though her eyes smiled a welcome she said nothing until Alvin had made himself comfortable---or as comfortable as he could be under that intense though friendly scrutiny. Then she sighed, and addressed Alvin in a low gentle voice.

"This is an occasion which does not often arise, so you will excuse me if I do not know the correct behaviour. But there are certain rights due to a guest, even if an unexpected one. Before we talk, there is something about which I should warn you. I can read your mind."

She smiled at Alvin's obvious consternation, and added quickly: "There is no need to let that worry you. No right is respected more strongly than that of mental privacy. I will enter your mind only if you invite me to. But it would not be fair to hide this fact from you, and it will explain why we find speech somewhat slow and difficult. It is not often used here."

This revelation, though slightly alarming, did not surprise Alvin. Once both men and machines had possessed this power and the unchanging machines could still read their masters' orders. But in Diaspar, man himself had lost the gift he had once shared with his slaves.

"I do not know what brought you from your world to ours," continued Seranis, "but if you are looking for life, your search has ended. Apart from Diaspar, there is only desert beyond our mountains."

It was strange that Alvin, who had questioned accepted beliefs so often before, did not doubt the words of Seranis. His only reaction was one of sadness that all his teaching had been so nearly true.

"Tell me about Lys," he begged. "Why have you been cut off from Diaspar for so long, when you seem to know so much about us?"

Seranis smiled at his eagerness.

"Presently," she said. "But first I would like to know something about you. Tell me how you found the way here, and why you came."

Haltingly at first, and then with growing confidence. Alvin told his story. He had never spoken with such freedom before; here at last was someone who would not laugh at his dreams because they knew those dreams were true. Once or twice Seranis interrupted him with swift questions, when he mentioned some aspect of Diaspar that was unfamiliar to her. It was hard for Alvin to realize that things which were part of his everyday life would be meaningless to someone who had never lived in the city and knew nothing of its complex culture and social organization. Seranis listened with such understanding that he took her comprehension for granted; not until much later did he realize that many other minds besides hers were listening to his words.

When he had finished, there was silence for a while. Then Seranis looked at him and said quietly: "Why did you come to Lys?"

Alvin glanced at her in surprise.

"I've told you," he said. "I wanted to explore the world. Everyone told me that there was only desert beyond the city, but I had to see for myself."

"And was that the only reason?"

Alvin hesitated. When at last he answered, it was not the indomitable explorer who spoke, but the lost child who had been born into an alien world.

"No," he said softly, "that wasn't the only reason---though I did not know it until now. I was lonely."

"Lonely? In Diaspar?" There was a smile on the lips of Seranis, but sympathy in her eyes, and Alvin knew that she expected no further answer.

Now that he had told his story, he waited for her to keep her share of the bargain. Presently Seranis rose to her feet and began to pace to and fro on the roof.

"I know the questions you wish to ask," she said. "Some of them I can answer, but it would be wearisome to do it in words. If you will open your mind to me, I will tell you what you need to know. You can trust me: I will take nothing from you without your permission."

"What do you want me to do?" said Alvin cautiously.

"Will yourself to accept my help---look at my eyes---and forget everything," commanded Seranis.

Alvin was never sure what happened then. There was a total eclipse of all his senses, and though he could never remember acquiring it, when he looked into his mind the knowledge was there.

He saw back into the past, not clearly, but as a man on some high mountain might look out across a misty plain. He understood that Man had not always been a city dweller, and that since the machines gave him freedom from toil there had always been a rivalry between two different types of civilization. In the Dawn of Ages there had been thousands of cities, but a large part of mankind had preferred to live in relatively small communities. Universal transport and instantaneous communication had given them all the contact they required with the rest of the world, and they felt no need to live huddled together with millions of their fellows.

Lys had been little different, in the early days, from hundreds or other communities. But gradually, over the ages, it developed an independent culture which was one of the highest that mankind had ever known. It was a culture based largely upon the direct use of mental power, and this set it apart from the rest of human society, which came to rely more and more upon machines.

Through the aeons, as they advanced along their different roads, the gulf between Lys and the cities widened. It was bridged only in times of great crisis; when the Moon was falling, its destruction was carried out by the scientists of Lys. So also was the defence of Earth against the Invaders, who were held at bay in the final Battle of Shalmirane.

That great ordeal exhausted mankind; one by one the cities died and the desert rolled over them. As the population fell, humanity began the migration that was to make Diaspar the last and greatest of all cities.

Most of these changes did not affect Lys, but it had its own battle to fight---the battle against the desert. The natural barrier of the mountains was not enough, and many ages passed before the great oasis was made secure. The picture was blurred here, perhaps deliberately. Alvin could not see what had been done to give Lys the virtual eternity that Diaspar had achieved.

The voice of Seranis seemed to come to him from a great distance---yet it was not her voice alone, for it was merged into a symphony of words, as though many other tongues were chanting in unison with hers.

"That, very briefly, is our history. You will see that even in the Dawn Ages we had little to do with the cities, though their people often came into our land. We never hindered them, for many of our greatest men came from outside, but when the cities were dying we did not wish to be involved in their downfall. With the ending of air transport there was only one way into Lys---the carrier system from Diaspar. It was closed at your end, when the park was built---and you forgot us, though we have never forgotten you.

"Diaspar has surprised us. We expected it to go the way of all other cities, but instead it has achieved a stable culture that may last as long as Earth. It is not a culture that we admire, yet we are glad that those who wish to escape have been able to do so. More than you might think have made the journey, and they have almost always been outstanding men who brought something of value with them when they came to Lys."

The voice faded; the paralysis of Alvin's senses ebbed away and he was himself again. He saw with astonishment that the sun had fallen far below the trees and that the eastern sky already held a hint of night. Somewhere a great bell vibrated with a throbbing boom that pulsed slowly into silence, leaving the air tense with mystery and premonition. Alvin found himself trembling slightly, not with the first touch of the evening's chill, but through sheer awe and wonder at all that he had learned. It was very late, and he was far from home. He had a sudden need to see his friends again, and to be among the familiar sights and scenes of Diaspar.

"I must return," he said. "Khedron---my parents---they will be expecting me."

That was not wholly true; Khedron would certainly be wondering what had happened to him, but as far as Alvin was aware no one else knew that he had left Diaspar. He could not have explained the reason for this mild deceit, and was slightly ashamed or himself as soon as he had uttered the words.

Seranis looked at him thoughtfully.

"I am afraid it is not as easy as that," she said.

"What do you mean?" asked Alvin. "Won't the carrier that brought me here take me back again?" He still refused to face the idea that he might be held in Lys against his will, though the idea had briefly crossed his mind.

For the first time, Seranis seemed slightly ill at ease.

"We have been talking about you," she said---not explaining who the "we" might be, nor exactly how they had consulted together. "If you return to Diaspar, the whole city will know about us. Even if you promise to say nothing, you would find it impossible to keep our secret."

"Why should you wish it kept?" asked Alvin. "Surely it would be a good thing for both our peoples if they could meet again."

Seranis looked displeased.

"We do not think so," she said. "If the gates were opened, our land would be flooded with the idly curious and the sensation seekers. As it is now, only the best of your people have ever reached us."

This reply radiated so much unconscious superiority, yet was based on such false assumptions, that Alvin felt his annoyance quite eclipse his alarm.

"That isn't true," he said flatly. "I do not believe you would find another person in Diaspar who could leave the city, even if he wanted to---even if he knew that there was somewhere to go. If you let me return, it would make no difference to Lys."

"It is not my decision," explained Seranis, "and you underestimate the powers of the mind if you think that the barriers that keep your people inside their city can never be broken. However, we do not wish to hold you here against your will, but if you return to Diaspar we must erase all memories of Lys from your mind." She hesitated for a moment. "This has never risen before; all your predecessors came here to stay."

Here was a choice that Alvin refused to accept. He wanted to explore Lys, to learn all its secrets, to discover the ways in which they differed from his own home, but equally he was determined to return to Diaspar, so that he could prove to his friends that he had been no idle dreamer. He could not understand the reasons prompting this desire for secrecy; even if he had, it would not have made any difference in his behaviour.

He realized that he must play for time or else convince Seranis that what she asked him was impossible. "Khedron knows where I am," he said. "You cannot erase his memories."

Seranis smiled. It was a pleasant smile, and one that in any other circumstances would have been friendly enough. But behind it Alvin glimpsed, for the first time, the presence of overwhelming and implacable power.

"You underestimate us, Alvin," she replied. "That would be very easy. I can reach Diaspar more quickly than I can cross Lys. Other men have come here before, and some of them told their friends where they were going. Yet those friends forget them, and they vanished from the history of Diaspar."

Alvin had been foolish to ignore this possibility, though it was obvious, now that Seranis had pointed it out. He wondered how many times, in the millions of years since the two cultures were separated, men from Lys had gone into Diaspar in order to preserve their jealously guarded secret. And he wondered just how extensive were the mental powers which these strange people possessed and did not hesitate to use.

Was it safe to make any plans at all? Seranis had promised that she would not read his mind without his consent, but he wondered if there might be circumstances in which that promise would not be kept.

"Surely," he said, "you don't expect me to make the decision at once. Cannot I see something of your country before I make my choice?"

"Of course," replied Seranis. "You can stay here as long as you wish, and still return to Diaspar eventually if you change your mind. But if you can decide within the next few days, it will be very much easier. You do not want your friends to be worried, and the longer you are missing the harder it will be for us to make the necessary adjustments."

Alvin could appreciate that; he would like to know just what those "adjustments" were. Presumably someone from Lys would contact Khedron---without the Jester ever being aware of it---and tamper with his mind. The fact of Alvin's disappearance could not be concealed, but the information that he and Khedron had discovered could be obliterated. As the ages passed, Alvin's name would join those of the other Uniques who had mysteriously vanished without trace and had then been forgotten.

There were many mysteries here, and he seemed no closer to solving any of them. Was there any purpose behind the curious, one-sided relationship between Lys and Diaspar, or was it merely a historical accident? Who and what were the Uniques, and if the people from Lys could enter Diaspar, why had they not cancelled the memory circuits that held the clue to their existence? Perhaps that was the only question to which Alvin could give a plausible answer. The Central Computer might be too stubborn an opponent to tackle, and would hardly be affected by even the most advanced of mental techniques.

He put these problems aside; one day, when he had learned a great deal more, he might have some chance of answering them. It was idle to speculate, to build pyramids of surmise on a foundation of ignorance.

"Very well," he said, though not too graciously, for he was still annoyed that this unexpected obstacle had been placed in his path. "I'll give you my answer as soon as I can, if you will show me what your land is like."

"Good," said Seranis, and this time her smile held no hidden threat. "We are proud of Lys, and it will be a pleasure to show you how men can live without the aid of cities. Meanwhile, there is no need for you to worry---your friends will not be alarmed by your absence. We shall see to that, if only for our own protection."

It was the first time Seranis had ever made a promise that she could not keep.

ALYSTRA had found it very easy to follow Alvin and Khedron without their knowledge. They seemed in a great hurry---something which in itself was most unusual---and never looked back. It had been an amusing game to pursue them along the moving ways, hiding in the crowds yet always keeping them in sight. Toward the end their goal had been obvious; when they left the pattern of streets and went into the park, they could only be heading for the Tomb of Yarlan Zey. The park contained no other buildings, and people in such eager haste as Alvin and Khedron would not be interested merely in enjoying the scenery.

Because there was no way of concealing herself on the last few hundred yards to the Tomb, Alystra waited until Khedron and Alvin had disappeared into the marbled gloom. Then, as soon as they were out of sight, she hurried up the grass-covered slope. She felt fairly sure that she could hide behind one of the great pillars long enough to discover what Alvin and Khedron were doing; it did not matter if they detected her after that.

The Tomb consisted of two concentric rings of columns, enclosing a circular courtyard. Except in one sector, the columns screened off the interior completely, and Alystra avoided approaching through this opening, but entered the Tomb from the side. She cautiously negotiated the first ring of columns, saw that there was no one in sight, and tiptoed across to the second. Through the gaps, she could see Yarlan Zey looking out through the entrance, across the park he had built, and beyond that to the city over which he had watched for so many ages.

And there was no one else in all this marble solitude. The Tomb was empty.

+++

At that moment, Alvin and Khedron were a hundred feet underground, in a small, boxlike room whose walls seemed to be flowing steadily upward. That was the only indication of movement; there was no trace of vibration to show that they were sinking swiftly into the earth, descending toward a goal that even now neither of them fully understood.

It had been absurdly easy, for the way had been prepared for them. (By whom? wondered Alvin. By the Central Computer? Or by Yarlan Zey himself, when he transformed the city?) The monitor screen had shown them the long, vertical shaft plunging into the depths, but they had followed its course only a little way when the image had blanked out. That meant, Alvin knew, that they were asking for information that the monitor did not possess, and perhaps never had possessed.

He had scarcely framed this thought when the screen came to life once more. On it appeared a brief message, printed in the simplified script that machines had used to communicate with men ever since they had achieved intellectual equality:

STAND WHERE THE STATUE GAZES---AND REMEMBER: DIASPAR WAS NOT ALWAYS THUS

The last five words were in larger type, and the meaning of the entire message was obvious to Alvin at once. Mentally framed code messages had been used for ages to unlock doors or set machines in action. As for "Stand where the statue gazes"---that was really too simple.

"I wonder how many people have read this message?" said Alvin thoughtfully.

"Fourteen, to my knowledge," replied Khedron. "And there may have been others." He did not amplify this rather cryptic remark, and Alvin was in too great a hurry to reach the park to question him further.

They could not be certain that the mechanisms would still respond to the triggering impulse. When they reached the Tomb, it had taken them only a moment to locate the single slab, among all those paving the floor, upon which the gaze of Yarlan Zey was fixed. It was only at first sight that the statue seemed to be looking out across the city; if one stood directly in front of it, one could see that the eyes were downcast and that the elusive smile was directed toward a spot just inside the entrance to the Tomb. Once the secret was realized, there could be no doubt about it. Alvin moved to the next slab, and found that Yarlan Zey was no longer looking toward him.

He rejoined Khedron, and mentally echoed the words that the Jester spoke aloud: "Diaspar was not always thus." Instantly, as if the millions of years that had lapsed since their last operation had never existed, the waiting machines responded. The great slab of stone on which they were standing began to carry them smoothly into the depths.

Overhead, the patch of blue suddenly flickered out of existence. The shaft was no longer open; there was no danger that anyone should accidentally stumble into it. Alvin wondered fleetingly if another slab of stone had somehow been materialized to replace the one now supporting him and Khedron, then decided against it. The original slab probably still paved the Tomb; the one upon which they were standing might only exist for infinitesimal fractions of a second, being continuously re-created at greater and greater depths in the earth to give the illusion of steady downward movement.

Neither Alvin nor Khedron spoke as the walls flowed silently past them. Khedron was once again wrestling with his conscience, wondering if this time he had gone too far. He could not imagine where this route might lead, if indeed it led anywhere. For the first time in his life, he began to understand the real meaning of fear.

Alvin was not afraid; he was too excited. This was the sensation he had known in the Tower of Loranne, when he had looked out across the untrodden desert and seen the stars conquering the night sky. He had merely gazed at the unknown then; he was being carried toward it now.

The walls ceased to flow past them. A patch of light appeared at one side of their mysteriously moving room, grew brighter and brighter, and was suddenly a door. They stepped through it, took a few paces along the short corridor beyond---and then were standing in a great circular cavern whose walls came together in a sweeping curve three hundred feet above their heads.

The column down whose interior they had descended seemed far too slim to support the millions of tons of rock above it; indeed, it did not seem to be an integral part of the chamber at all, but gave the impression of being an after-thought. Khedron, following Alvin's gaze, arrived at the same conclusion.

"This column," he said, speaking rather jerkily, as if anxious to find something to say, "was built simply to house the shaft down which we came. It could never have carried the traffic that must have passed through here when Diaspar was still open to the world. That came through those tunnels over there; I suppose you recognize what they are?"

Alvin looked toward the walls of the chamber, more than a hundred yards away. Piercing them at regular intervals were large tunnels, twelve of them, radiating in all directions exactly as the moving ways still did today. He could see that they sloped gently upward, and now he recognized the familiar grey surface of the moving ways. These were only the severed stumps of the great roads; the strange material that gave them life was now frozen into immobility. When the park had been built, the hub of the moving way system had been buried. But it had never been destroyed.

Alvin began to walk toward the nearest of the tunnels. He had gone only a few paces when he realized that something was happening to the ground beneath his feet. It was becoming transparent. A few more yards, and he seemed to be standing in midair without visible support. He stopped and stared down into the void beneath him.

"Khedron!" he called. "Come and look at this!"

The other joined him, and together they gazed at the marvel beneath their feet. Faintly visible, at an indefinite depth, lay an enormous map---a great network of lines converging toward a spot beneath the central shaft. They stared at it in silence for a moment; then Khedron said quietly: "You realize what this is?"

"I think so," replied Alvin. "It's a map of the entire transport system, and those little circles must be the other cities of Earth. I can just see names beside them, but they're too faint to read."

"There must have been some form of internal illumination once," said Khedron absently. He was tracing the lines beneath his feet, following them with his eyes out toward the walls of the chamber.

"I thought so!" he exclaimed suddenly. "Do you see how all these radiating lines lead toward the small tunnels?"

Alvin had noticed that besides the great arches of the moving ways there were innumerable smaller tunnels leading out of the chamber---tunnels that sloped downward instead of up.

Khedron continued without waiting for a reply.

"It would be hard to think of a simpler system. People would come down the moving ways, select the place they wished to visit, and then follow the appropriate line on the map."

"And what happened to them after that?" asked Alvin. Khedron was silent, his eyes searching out the mystery of those descending tunnels. There were thirty or forty of them, all looking exactly the same. Only the names on the map would have enabled one to distinguish between them, and those names were indecipherable now.

Alvin had wandered away and was circumnavigating the central pillar. Presently his voice came to Khedron, slightly muffled and overlaid with echoes from the walls of the chamber. "What is it?" called Khedron, not wishing to move, because he had nearly succeeded in reading one of the dimly visible groups of characters. But Alvin's voice was insistent, so he went to join him.

Far beneath was the other half of the great map, its faint webwork radiating to the points of the compass. This time, however, not all of it was too dim to be clearly seen, for one of the lines---and only one---was brilliantly illuminated. It seemed to have no connection with the rest of the system, and pointed like a gleaming arrow to one of the downward-sloping tunnels. Near its end the line transfixed a circle of golden light, and against that circle was the single word LYS. That was all.

For a long time Alvin and Khedron stood gazing down at that silent symbol. To Khedron it was a challenge he knew he could never accept---and which, indeed, he would rather did not exist. But to Alvin it hinted at the fulfillment of all his dreams; though the word Lys meant nothing to him, he let it roll around his mouth, tasting its sibilance like some exotic flavour. The blood was pounding in his veins, and his cheeks were flushed as by a fever. He stared around this great concourse, trying to imagine it as it had been in the ancient days, when air transport had come to an end but the cities of Earth still had contact with one another. He thought of the countless millions of years that had passed with the traffic steadily dwindling and the lights on the great map dying one by one, until at last only this single line remained. How long, he wondered, had it gleamed there among its darkened companions, waiting to guide the steps that never came, until Yarlan Zey had sealed the moving ways and closed Diaspar against the world?

And that had been a billion years ago. Even then, Lys must have lost touch with Diaspar. It seemed impossible that it could have survived; perhaps, after all, the map meant nothing now.

Khedron broke into his reverie at last. He seemed nervous and ill at ease, not at all like the confident and self-assured person that he had always been in the city above.

"I do not think that we should go any farther now," he said. "It may not be safe until---until we are more prepared."

There was wisdom in this, but Alvin recognized the underlying note of fear in Khedron's voice. Had it not been for that, he might have been sensible, but a too-acute awareness of his own valour, combined with a contempt for Khedron's timidity, drove Alvin onward. It seemed foolish to have come so far, only to turn back when the goal might be in sight.

"I'm going down that tunnel," he said stubbornly, as if challenging Khedron to stop him. "I want to see where it leads." He set off resolutely, and after a moment's hesitation the Jester followed him along the arrow of light that burned beneath their feet.

As they stepped into the tunnel, they felt the familiar tug of the peristaltic field, and in a moment were being swept effortlessly into the depths. The journey lasted scarcely a minute; when the field released them they were standing at one end of a long narrow chamber in the form of a half-cylinder. At its distant end, two dimly lit tunnels stretched away toward infinity.

Men of almost every civilization that had existed since the Dawn would have found their surroundings completely familiar, yet to Alvin and Khedron this was a glimpse of another world. The purpose of the long, streamlined machine that lay aimed like a projectile at the far tunnel was obvious, but that made it none the less novel. Its upper portion was transparent, and looking through the walls Alvin could see rows of luxuriously appointed seats. There was no sign of any entrance, and the entire machine was floating about a foot above a single metal rod that stretched away into the distance, disappearing in one of the tunnels. A few yards away another rod led to the second tunnel, but no machine floated above it. Alvin knew, as surely as if he had been told, that somewhere beneath unknown, far-off Lys, that second machine was waiting in another such chamber as this.

Khedron began to talk, a little too swiftly.

"What a peculiar transport system! It could only handle a hundred people at a time, so they could not have expected much traffic. And why did they go to all this trouble to bury themselves in the Earth if the skies were still open? Perhaps the Invaders would not even permit them to fly, though I find that hard to believe. Or was this built during the transition period, while men still travelled but did not wish to be reminded of space? They could go from city to city, and never see the sky and the stars." He gave a nervous laugh. "I feel sure of one thing, Alvin. When Lys existed, it was much like Diaspar. All cities must be essentially the same. No wonder that they were all abandoned in the end, and merged into Diaspar. What was the point of having more than one?"

Alvin scarcely heard him. He was busy examining the long projectile, trying to find the entrance. If the machine was controlled by some central or verbal code order, he might never be able to make it obey him, and it would remain a maddening enigma for the rest of his life.

The silently opening door took him completely unawares. There was no sound, no warning when a section of the wall simply faded from sight and the beautifully designed interior lay open before his eyes.

This was the moment of choice. Until this instant, he had always been able to turn back if he wished. But if he stepped inside that welcoming door, he knew what would happen, though not where it would lead. He would no longer be in control of his own destiny, but would have placed himself in the keeping of unknown forces.

He scarcely hesitated. He was afraid to hold back, being fearful that if he waited too long this moment might never come again---or that if it did, his courage might not match his desire for knowledge. Khedron opened his mouth in anxious protest, but before he could speak, Alvin had stepped through the entrance. He turned to face Khedron, who was standing framed in the barely visible rectangle of the doorway, and for a moment there was a strained silence while each waited for the other to speak.

The decision was made for them. There was a faint flicker of translucence, and the wall of the machine had closed again. Even as Alvin raised his hand in farewell, the long cylinder started to ease itself forward. Before it had entered the tunnel, it was already moving faster than a man could run.

There had been a time when, every day, millions of men made such journeys, in machines basically the same as this, as they shuttled between their homes and their humdrum jobs. Since that far-off day, Man had explored the Universe and returned again to Earth---had won an empire, and had it wrestled from his grasp. Now such a journey was being made again, in a machine wherein legions of forgotten and unadventurous men would have felt completely at home.

And it was to be the most momentous journey any human being had undertaken for a billion years.

+++

Alystra had searched the Tomb a dozen times, though once was quite sufficient, for there was nowhere anyone could hide. After the first shock of surprise, she had wondered if what she had followed across the park had not been Alvin and Khedron at all, but only their projections. But that made no sense; projections were materialized at any spot one wished to visit, without the trouble of going there in person. No sane person would "walk" his projected image a couple of miles, taking half an hour to reach his destination, when he could be there instantly. No; it was the real Alvin and the real Khedron that she had followed into the Tomb.

Somewhere, then, there must be a secret entrance. She might as well look for it while she was waiting for them to come back.

As luck would have it, she missed Khedron's reappearance, for she was examining a column behind the statue when he emerged on the other side of it. She heard his footsteps, turned toward him, and saw at once that he was alone.

"Where is Alvin?" she cried.

It was some time before the Jester answered. He looked distraught and irresolute, and Alystra had to repeat her question before he took any notice of her. He did not seem in the least surprised to find her there.

"I do not know where he is," he answered at last. "I can only tell you that he is on his way to Lys. Now you know as much as I do."

It was never wise to take Khedron's words at their face value. But Alystra needed no further assurance that the Jester was not playing his role today. He was telling her the truth---whatever it might mean.

THE image on the monitor screen faded as Alvin raised his hands from the control panel and cleared the circuits. For a moment he sat quite motionless, looking into the blank rectangle that had occupied all his conscious mind for so many weeks. He had circumnavigated his world; across that screen had passed every square foot of the outer wall of Diaspar. He knew the city better than any living man save perhaps Khedron; and he knew now that there was no way through the walls.

The feeling that possessed him was not mere despondency; he had never really expected that it would be as easy as this, that he would find what he sought at the first attempt. What was important was that he had eliminated one possibility. Now he must deal with the others.

He rose to his feet and walked over to the image of the city which almost filled the chamber. It was hard not to think of it as an actual model, though he knew that in reality it was no more than an optical projection of the pattern in the memory cells he had been exploring. When he altered the monitor controls and set his viewpoint moving through Diaspar, a spot of light would travel over the surface of this replica, so that he could see exactly where he was going. It had been a useful guide in the early days, but he soon had grown so skillful at setting the co-ordinates that he had not needed this aid.

The city lay spread out beneath him; he looked down upon it like a god. Yet he scarcely saw it as he considered, one by one, the steps he should now take.

If all else failed, there was one solution to the problem. Diaspar might be held in a perpetual stasis by its eternity circuits, frozen forever according to the pattern in the memory cells, but that pattern could itself be altered, and the city would then change with it. It would be possible to redesign a section of the outer wall so that it contained a doorway, feed this pattern into the monitors, and let the city reshape itself to the new conception.

Alvin suspected that the large areas of the monitor control board whose purpose Khedron had not explained to him were concerned with such alterations. It would be useless to experiment with them; controls that could alter the very structure of the city were firmly locked and could be operated only with the authority of the Council and the approval of the Central Computer. There was very little chance that the Council would grant him what he asked, even if he were prepared for decades or even centuries of patient pleading. That was not a prospect that appealed to him in the least.

He turned his thoughts toward the sky. Sometimes he had imagined, in fantasies which he was half-ashamed to recall, that he had regained the freedom of the air which man had renounced so long ago. Once, he knew, the skies of Earth had been filled with strange shapes. Out of space the great ships had come, bearing unknown treasures, to berth at the legendary Port of Diaspar. But the Port had been beyond the limits of the city; aeons ago it had been buried by the drifting sand. He could dream that somewhere in the mazes of Diaspar a flying machine might still be hidden, but he did not really believe it. Even in the days when small, personal flyers had been in common use, it was most unlikely that they had ever been allowed to operate inside the limits of the city.

For a moment he lost himself in the old, familiar dream. He imagined that he was master of the sky, that the world lay spread out beneath him, inviting him to travel where he willed. It was not the world of his own time that he saw, but the lost world of the dawn---a rich and living panorama of hills and lakes and forests. He felt a bitter envy of his unknown ancestors, who had flown with such freedom over all the earth and who had let its beauty die.

This mind-drugging reverie was useless; he tore himself back to the present and to the problem at hand. If the sky was unattainable and the way by land was barred, what remained?

Once again he had come to the point when he needed help, when he could make no further progress by his own efforts. He disliked admitting the fact, but was honest enough not to deny it. Inevitably, his thoughts turned to Khedron.

Alvin had never been able to decide whether he liked the Jester. He was very glad that they had met, and was grateful to Khedron for the assistance and implicit sympathy he had given him on his quest. There was no one else in Diaspar with whom he had so much in common, yet there was some element in the other's personality that jarred upon him. Perhaps it was Khedron's air of ironic detachment, which sometimes gave Alvin the impression that he was laughing secretly at all his efforts, even while he seemed to be doing his best to help. Because of this, as well as his own natural stubbornness and independence, Alvin hesitated to approach the Jester except as a last resort.

They arranged to meet in a small, circular court not far from Council Hall. There were many such secluded spots in the city, perhaps only a few yards from some busy thoroughfare, yet completely cut off from it. Usually they could be reached only on foot after a rather roundabout walk; sometimes, indeed, they were at the centre of skillfully contrived mazes which enhanced their isolation. It was rather typical of Khedron that he should have chosen such a place for a rendezvous.

The court was little more than fifty paces across, and was in reality located deep within the interior of some great building. Yet it appeared to have no definite physical limits, being bounded by a translucent blue-green material which glowed with a faint internal light. However, though there were no visible limits, the court had been so laid out that there was no danger of feeling lost in infinite space. Low walls, less than waist high and broken at intervals so that one could pass through them, managed to give the impression of safe confinement without which no one in Diaspar could ever feel entirely happy.

Khedron was examining one of these walls when Alvin arrived. It was covered with an intricate mosaic of coloured tiles, so fantastically involved that Alvin did not even attempt to unravel it.

"Look at this mosaic, Alvin," said the Jester. "Do you notice anything strange about it?"

"No," confessed Alvin after a brief examination. "I don't care for it---but there's nothing strange about that."

Khedron ran his fingers over the coloured tiles. "You are not very observant," he said. "Look at these edges here---see how they become rounded and softened. This is something that one very seldom sees in Diaspar, Alvin. It is wear---the crumbling away of matter under the assault of time. I can remember when this pattern was new, only eighty thousand years ago, in my last lifetime. If I come back to this spot a dozen lives from now, these tiles will have been worn completely away."

"I don't see anything very surprising about that," answered Alvin. "There are other works of art in the city not good enough to be preserved in the memory circuits, but not bad enough to be destroyed outright. One day, I suppose, some other artist will come along and do a better job. And his work won't be allowed to wear out."

"I knew the man who designed this wall," said Khedron, his fingers still exploring the cracks in the mosaic. "Strange that I can remember that fact, when I don't recall the man himself. I could not have liked him, so I must have erased him from my mind." He gave a short laugh. "Perhaps I designed it myself, during one of my artistic phases, and was so annoyed when the city refused to make it eternal that I decided to forget the whole affair. There---I knew that piece was coming loose!" He had managed to pull out a single flake of golden tile, and looked very pleased at this minor sabotage. He threw the fragment on the ground, adding, "Now the maintenance robots will have to do something about it!"

There was a lesson for him here, Alvin knew. That strange instinct known as intuition, which seemed to follow short cuts not accessible to mere logic, told him that. He looked at the golden shard lying at his feet, trying to link it somehow to the problem that now dominated his mind.

It was not hard to find the answer, once he realized that it existed.

"I see what you are trying to tell me," he said to Khedron. "There are objects in Diaspar that aren't preserved in the memory circuits, so I could never find them through the monitors at Council Hall. If I was to go there and focus on this court, there would be no sign of the wall we're sitting on."

"I think you might find the wall. But there would be no mosaic on it."

"Yes, I can see that," said Alvin, too impatient now to bother about such hairsplitting. "And in the same way, parts of the city might exist that had never been preserved in the eternity circuits, but which hadn't yet worn away. Still, I don't really see how that helps me. I know that the outer wall exists---and that it has no openings in it."

"Perhaps there is no way out," answered Khedron. "I can promise you nothing. But I think there is still a great deal that the monitors can teach us---if the Central Computer will let them. And it seems to have taken rather a liking to you."

Alvin pondered over this remark on their way to Council Hall. Until now, he had assumed that it was entirely through Khedron's influence that he had been able to gain access to the monitors. It had not occurred to him that it might be through some intrinsic quality of his own. Being a Unique had many disadvantages; it was only right that it should have some compensations.

The unchanging image of the city still dominated the chamber in which Alvin had spent so many hours. He looked at it now with a new understanding; all that he saw here existed---but all of Diaspar might not be mirrored. Yet, surely, any discordancies must be trivial, and, as far as he could see, undetectable.

"I attempted to do this many years ago," said Khedron, as he sat down at the monitor desk, "but the controls were locked against me. Perhaps they will obey me now."

Slowly, and then with mounting confidence as he regained access to long-forgotten skills, Khedron's fingertips moved over the control desk, resting for a moment at the nodal points in the sensitive grid buried in the panel before him.

"I think that's correct," he said at last. "Anyway we'll soon see."

The screen glowed into life, but instead of the picture that Alvin had expected, there appeared a somewhat baffling message:

REGRESSION WILL COMMENCE AS SOON AS YOU HAVE SET RATE CONTROL

"Foolish of me," muttered Khedron. "I got everything else right and forgot the most important thing of all." His fingers now moved with a confident assurance over the board, and as the message faded from the screen he swung around in his seat so that he could look at the replica of the city.

"Watch this, Alvin," he said. "I think we are both going to learn something new about Diaspar."

Alvin waited patiently, but nothing happened. The image of the city floated there before his eyes in all its familiar wonder and beauty---though he was conscious of neither now. He was about to ask Khedron what he should look for when a sudden movement caught his attention, and he turned his head quickly to follow it. It had been no more than a half-glimpsed flash or flicker, and he was too late to see what had made it. Nothing had altered; Diaspar was just as he had always known it. Then he saw that Khedron was watching him with a sardonic smile, so he looked again at the city. This time, the thing happened before his eyes.

One of the buildings at the edge of the park suddenly vanished, and was replaced instantly by another of quite different design. The transformation was so abrupt that had Alvin been blinking he would have missed it. He stared in amazement at the subtly altered city, but even during the first shock of astonishment his mind was seeking for the answer. He remembered the words that had appeared on the monitor screen---REGRESSION WILL COMMENCE---and he knew at once what was happening.

"That's the city as it was thousands of years ago," he said to Khedron. "We're going back in time."

"A picturesque but hardly accurate way of putting it," replied the Jester. "What is actually happening is that the monitor is remembering the earlier versions of the city. When any modifications were made, the memory circuits were not simply emptied; the information in them was taken to subsidiary storage units, so that it could be recalled whenever needed. I have set the monitor to regress through those units at the rate of a thousand years a second. Already, we're looking at the Diaspar of half a million years ago. We'll have to go much farther back than that to see any real changes---I'll increase the rate."

He turned back to the control board, and even as he did so, not one building but a whole block whipped out of existence and was replaced by a large oval amphitheatre.

"Ah, the Arena!" said Khedron. "I can remember the fuss when we decided to get rid of that. It was hardly ever used, but a great many people felt sentimental about it."

The monitor was now recalling its memories at a far higher rate; the image of Diaspar was receding into the past at millions of years a minute, and changes were occurring so rapidly that the eye could not keep up with them. Alvin noticed that the alterations to the city appeared to come in cycles; there would be a long period of stasis, then a whole rash of rebuilding would break out, followed by another pause. It was almost as if Diaspar were a living organism, which had to regain its strength after each explosion of growth.

Through all these changes, the basic design of the city had not altered. Buildings came and went, but the pattern of streets seemed eternal, and the park remained as the green heart of Diaspar. Alvin wondered how far back the monitor could go. Could it return to the founding of the city, and pass through the veil that sundered known history from the myths and legends of the Dawn?

Already they had gone five hundred million years into the past. Outside the walls of Diaspar, beyond the knowledge of the monitors, it would be a different Earth. Perhaps there might be oceans and forests, even other cities which Man had not yet deserted in the long retreat to his final home.

The minutes drifted past, each minute an aeon in the little universe of the monitors. Soon, thought Alvin, the earliest of all these stored memories must be reached and the regression would end. But fascinating though this lesson was, he did not see how it could help him to escape from the city as it was here and now.

With a sudden, soundless implosion, Diaspar contracted to a fraction of its former size. The park vanished; the boundary wall of linked, titanic towers instantly evaporated. This city was open to the world, for the radial roads stretched out to the limits of the monitor image without obstruction. Here was Diaspar as it had been before the great change came upon mankind.

"We can go no farther," said Khedron, pointing to the monitor screen. On it had appeared the words: REGRESSION CONCLUDED. "This must be the earliest version of the city that has been preserved in the memory cells. Before that, I doubt if the eternity circuits were used, and the buildings were allowed to wear out naturally."

For a long time, Alvin stared at this model of the ancient city. He thought of the traffic those roads had borne, as men came and went freely to all the corners of the world---and to other worlds as well. Those men were his ancestors; he felt a closer kinship to them than to the people who now shared his life. He wished that he could see them and share their thoughts, as they moved through the streets of that billion-year remote Diaspar. Yet those thoughts could not have been happy ones, for they must have been living then beneath the shadow of the Invaders. In a few more centuries, they were to turn their faces from the glory they had won and build a wall against the Universe.

Khedron ran the monitor backward and forward a dozen times through the brief period of history that had wrought the transformation. The change from a small open city to a much larger closed one had taken little more than a thousand years. In that time, the machines that had served Diaspar so faithfully must have been designed and built, and the knowledge that would enable them to carry out their tasks had been fed into their memory circuits. Into the memory circuits, also, must have gone the essential patterns of all the men who were now alive, so that when the right impulse called them forth again they could be clothed in matter and would emerge reborn from the Hall of Creation. In some sense, Alvin realized, he must have existed in that ancient world. It was possible, of course, that he was completely synthetic---that his entire personality had been designed by artist-technicians who had worked with tools of inconceivable complexity toward some clearly envisaged goal. Yet he thought it more likely that he was a composite of men who had once lived and walked on Earth.

Very little of the old Diaspar had remained when the new city was created; the park had obliterated it almost completely. Even before the transformation, there had been a small, grass-covered clearing at the centre of Diaspar, surrounding the junction of all the radial streets. Afterward it had expanded tenfold, wiping out streets and buildings alike. The Tomb of Yarlan Zey had been brought into existence at this time, replacing a very large circular structure which had previously stood at the meeting point of all the streets. Alvin had never really believed the legends of the Tomb's antiquity, but now it seemed that they were true.

"I suppose," said Alvin, struck by a sudden thought, "that we can explore this image, just as we explored the image of today's Diaspar?"

Khedron's fingers flickered over the monitor control board, and the screen answered Alvin's question. The long-vanished city began to expand before his eyes as his viewpoint moved along the curiously narrow streets. This memory of the Diaspar that once had been was still as sharp and clear as the image of the city he lived in today. For a billion years, the information circuits had held it in ghostly pseudo-existence, waiting for the moment when someone should call it forth again. And it was not, thought Alvin, merely a memory he was seeing now. It was something more complex than that---it was the memory of a memory.

He did not know what he could learn from it, and whether it could help him in his quest. No matter; it was fascinating to look into the past and to see a world that had existed in the days when men still roamed among the stars. He pointed to the low, circular building that stood at the city's heart.

"Let's start there," he told Khedron. "That seems as good a place as any to begin."

Perhaps it was sheer luck; perhaps it was some ancient memory; perhaps it was elementary logic. It made no difference, since he would have arrived at this spot sooner or later---this spot upon which all the radial streets of the city converged.

It took him ten minutes to discover that they did not meet here for reasons of symmetry alone---ten minutes to know that his long search had met its reward.

"YOU took your time," said Khedron, "but I knew you would call sooner or later."

This confidence annoyed Alvin; he did not like to think that his behaviour could be predicted so accurately. He wondered if the Jester had watched all his fruitless searching and knew exactly what he had been doing.

"I am trying to find a way out of the city," he said bluntly. "There must be one, and I think you could help me find it."

Khedron was silent for a moment. There was still time, if he wished, to turn back from the road that stretched before him, and which led into a future beyond all his powers of prophecy. No one else would have hesitated; no other man in the city, even if he had the power, would have dared to disturb the ghosts of an age that had been dead for millions of centuries. Perhaps there was no danger, perhaps nothing could alter the perpetual changelessness of Diaspar. But if there was any risk of something strange and new coming into the world, this might be the last chance to ward it off.

Khedron was content with the order of things as it was. True, he might upset that order from time to time---but only by a little. He was a critic, not a revolutionary. On the placidly flowing river of time, he wished only to make a few ripples: he shrank from diverting its course. The desire for adventure, other than that of the mind, had been eliminated from him as carefully and thoroughly as from all the other citizens of Diaspar.

Yet he still possessed, though it was almost extinguished, that spark of curiosity that was once Man's greatest gift. He was still prepared to take a risk.

He looked at Alvin and tried to remember his own youth, his own dreams of half a thousand years before. Any moment of his past that he cared to choose was still clear and sharp when he turned his memory upon it. Like beads upon a string, this life and all the ones before it stretched back through the ages; he could seize and re-examine any one he wished. Most of those older Khedrons were strangers to him now; the basic patterns might be the same, but the weight of experience separated him from them forever. If he wished, he could wash his mind clear of all his earlier incarnations, when next he walked back into the Hall of Creation to sleep until the city called him forth again. But that would be a kind of death, and he was not ready for that yet. He was still prepared to go on collecting all that life could offer, like a chambered nautilus patiently adding new cells to its slowly expanding spiral.

In his youth, he had been no different from his companions. It was not until he came of age and the latent memories of his earlier lives came flooding back that he had taken up the role for which he had been destined long ago. Sometimes he felt resentment that the intelligences which had contrived Diaspar with such infinite skill could even now, after all these ages, make him move like a puppet across their stage. Here, perhaps, was a chance of obtaining a long-delayed revenge. A new actor had appeared who might ring down the curtain for the last time on a play that already had seen far too many acts.

Sympathy, for one whose loneliness must be even greater than his own; an ennui produced by ages of repetition; and an impish sense of fun---these were the discordant factors that prompted Khedron to act.

"I may be able to help you," he told Alvin, "or I may not. I don't wish to raise any false hopes. Meet me in half an hour at the intersection of Radius 3 and Ring 2. If I cannot do anything else, at least I can promise you an interesting journey."

Alvin was at the rendezvous ten minutes ahead of time, though it was on the other side of the city. He waited impatiently as the moving ways swept eternally past him, bearing the placid and contented people of the city about their unimportant business. At last he saw the tall figure of Khedron appear in the distance, and a moment later he was for the first time in the physical presence of the Jester. This was no projected image; when they touched palms in the ancient greeting, Khedron was real enough.

The Jester sat down on one of the marble balustrades and regarded Alvin with a curious intentness.

"I wonder," he said, "if you know what you are asking. And I wonder what you would do if you obtained it. Do you really imagine that you could leave the city, even if you found a way?"

"I am sure of it," replied Alvin, bravely enough, though Khedron could sense the uncertainty in his voice.

"Then let me tell you something which you may not know. You see those towers there?" Khedron pointed to the twin peaks of Power Central and Council Hall, staring at each other across a canyon a mile deep. "Suppose I were to lay a perfectly firm plank between those two towers---a plank only six inches wide. Could you walk across it?"

Alvin hesitated.

"I don't know," he answered. "I wouldn't like to try."

"I'm quite sure you could never do it. You'd get giddy and fall off before you'd gone a dozen paces. Yet if that same plank was supported just clear of the ground, you'd be able to walk along it without difficulty."

"And what does that prove?"

"A simple point I'm trying to make. In the two experiments I've described, the plank would be exactly the same in both cases. One of those wheeled robots you sometimes meet could cross it just as easily if it was bridging those towers as if it was laid along the ground. We couldn't, because we have a fear of heights. It may be irrational, but it's too powerful to be ignored. It is built into us; we are born with it.

"In the same way, we have a fear of space. Show any man in Diaspar a road out of the city---a road that might be just like this road in front of us now---and he could not go far along it. He would have to turn back, as you would turn back if you started to cross a plank between those towers."

"But why?" asked Alvin. "There must have been a time----"

"I know, I know," said Khedron. "Men once went out over the whole world, and to the stars themselves. Something changed them and gave them this fear with which they are now born. You alone imagine that you do not possess it. Well, we shall see. I'm taking you to Council Hall."

The Hall was one of the largest buildings in the city, and was almost entirely given over to the machines that were the real administrators of Diaspar. Not far from its summit was the chamber where the Council met on those infrequent occasions when it had any business to discuss.

The wide entrance swallowed them up, and Khedron strode forward into the golden gloom. Alvin had never entered Council Hall before; there was no rule against it---there were few rules against anything in Diaspar---but like everyone else he had a certain half-religious awe of the place. In a world that had no gods, Council Hall was the nearest thing to a temple.

Khedron never hesitated as he led Alvin along corridors and down ramps that were obviously made for wheeled machines, not human traffic. Some of these ramps zigzagged down into the depths at such steep angles that it would have been impossible to keep a footing on them had not gravity been twisted to compensate for the slope.

They came at last to a closed door, which slid silently open as they approached, then barred their retreat. Ahead was another door, which did not open as they came up to it. Khedron made no move to touch the door, but stood motionless in front of it. After a short pause, a quiet voice said: "Please state your names."

"I am Khedron the Jester. My companion is Alvin."

"And your business?"

"Sheer curiosity."

Rather to Alvin's surprise, the door opened at once. In his experience, if one gave facetious replies to machines it always led to confusion and one had to go back to the beginning. The machine that had interrogated Khedron must have been a very sophisticated one---far up in the hierarchy of the Central Computer.

They met no more barriers, but Alvin suspected that they had passed many tests of which he had no knowledge. A short corridor brought them out abruptly into a huge circular chamber with a sunken floor, and set in that floor was something so astonishing that for a moment Alvin was overwhelmed with wonder. He was looking down upon the entire city of Diaspar, spread out before him with its tallest buildings barely reaching to his shoulder.

He spent so long picking out familiar places and observing unexpected vistas that it was some time before he paid any notice to the rest of the chamber. Its walls were covered with a microscopically detailed pattern of black and white squares; the pattern itself was completely irregular, and when he moved his eyes quickly he got the impression that it was flickering swiftly, though it never changed. At frequent intervals around the chamber were manually controlled machines of some type, each complete with a vision screen and a seat for the operator.

Khedron let Alvin look his fill. Then he pointed to the diminutive city and said: "Do you know what that is?"

Alvin was tempted to answer, "A model, I suppose," but that answer was so obvious that he was sure it must be wrong. So he shook his head and waited for Khedron to answer his own question.

"You remember," said the Jester, "that I once told you how the city was maintained---how the Memory Banks hold its pattern frozen forever. Those Banks are all around us, with all their immeasurable store of information, completely defining the city as it is today. Every atom of Diaspar is somehow keyed, by forces we have forgotten, to the matrices buried in these walls."

He waved toward the perfect, infinitely detailed simulacrum of Diaspar that lay below them.

"That is no model; it does not really exist. It is merely the projected image of the pattern held in the Memory Banks, and therefore it is absolutely identical with the city itself. These viewing machines here enable one to magnify any desired portion, to look at it life size or larger. They are used when it is necessary to make alterations in the design, though it is a very long time since that was done. If you want to know what Diaspar is like, this is the place to come. You can learn more here in a few days than you would in a lifetime of actual exploring."

"It's wonderful," said Alvin. "How many people know that it exists?"

"Oh, a good many, but it seldom concerns them. The Council comes down here from time to time; no alterations to the city can be made unless they are all here. And not even then, if the Central Computer doesn't approve of the proposed change. I doubt if this room is visited more than two or three times a year."

Alvin wanted to know how Khedron had access to it, and then remembered that many of his more elaborate jests must have involved a knowledge of the city's inner mechanisms that could have come only from very profound study. It must be one of the Jester's privileges to go anywhere and learn anything; he could have no better guide to the secrets of Diaspar.

"What you are looking for may not exist," said Khedron, "but if it does, this is where you will find it. Let me show you how to operate the monitors."

For the next hour Alvin sat before one of the vision screens, learning to use the controls. He could select at will any point in the city, and examine it with any degree of magnification. Streets and towers and walls and moving ways flashed across the screen as he changed the co-ordinates; it was as though he was an all-seeing, disembodied spirit that could move effortlessly over the whole of Diaspar, unhindered by any physical obstructions.

Yet it was not, in reality, Diaspar that he was examining. He was moving through the memory cells, looking at the dream image of the city---the dream that had had the power to hold the real Diaspar untouched by time for a billion years. He could see only that part of the city which was permanent; the people who walked its streets were no part of this frozen image. For his purpose, that did not matter. His concern now was purely with the creation of stone and metal in which he was imprisoned, and not those who shared---however willingly---his confinement.

He searched for and presently found the Tower of Loranne, and moved swiftly through the corridors and passageways which he had already explored in reality. As the image of the stone grille expanded before his eyes, he could almost feel the cold wind that had blown ceaselessly through it for perhaps half the entire history of mankind, and that was blowing now. He came up to the grille, looked out---and saw nothing. For a moment the shock was so great that he almost doubted his own memory; had his vision of the desert been nothing more than a dream?

Then he remembered the truth. The desert was no part of Diaspar, and therefore no image of it existed in the phantom world he was exploring. Anything might lie beyond that grille in reality; this monitor screen could never show it.

Yet it could show him something that no living man had ever seen. Alvin advanced his viewpoint through the grille, out into the nothingness beyond the city. He turned the control which altered the direction of vision, so that he looked backward along the way that he had come. And there behind him lay Diaspar---seen from the outside.

To the computers, the memory circuits, and all the multitudinous mechanisms that created the image at which Alvin was looking, it was merely a simple problem of perspective. They "knew" the form of the city; therefore they could show it as it would appear from the outside. Yet even though he could appreciate how the trick was done, the effect on Alvin was overwhelming. In spirit, if not reality, he had escaped from the city. He appeared to be hanging in space, a few feet away from the sheer wall of the Tower of Loranne. For a moment he stared at the smooth grey surface before his eyes; then he touched the control and let his viewpoint drop toward the ground.

Now that he knew the possibilities of this wonderful instrument, his plan of action was clear. There was no need to spend months and years exploring Diaspar from the inside, room by room and corridor by corridor. From this new vantage point he could wing his way along the outside of the city, and could see at once any openings that might lead to the desert and the world beyond.

The sense of victory, of achievement, made him feel light-headed and anxious to share his joy. He turned to Khedron, wishing to thank the Jester for having made this possible. But Khedron was gone, and it took only a moment's thought to realize why.

Alvin was perhaps the only man in Diaspar who could look unaffected upon the images that were now drifting across the screen. Khedron could help him in his search, but even the Jester shared the strange terror of the Universe which had pinned mankind for so long inside its little world. He had left Alvin to continue his quest alone.

The sense of loneliness, which for a little while had lifted from Alvin's soul, pressed down upon him once more. But this was no time for melancholy; there was too much to do. He turned back to the monitor screen, set the image of the city wall drifting slowly across it, and began his search.

+++

Diaspar saw little of Alvin for the next few weeks, though only a few people noticed his absence. Jeserac, when he discovered that his erstwhile pupil was spending all his time at Council Hall instead of prowling around the frontier of the city, felt slightly relieved, imagining that Alvin could come to no trouble there. Eriston and Etania called his room once or twice, found that he was out and thought nothing of it. Alystra was a little more persistent.

For her own peace of mind, it was a pity that she had become infatuated with Alvin, when there were so many more suitable choices. Alystra had never had any difficulty in finding partners, but by comparison with Alvin all the other men she knew were nonentities, cast from the same featureless mould. She would not lose him without a struggle; his aloofness and indifference set a challenge which she could not resist.

Yet perhaps her motives were not entirely selfish, and were maternal rather than sexual. Though birth had been forgotten, the feminine instincts of protection and sympathy still remained. Alvin might appear to be stubborn and self-reliant and determined to have his own way, yet Alystra could sense his inner loneliness.

When she found that Alvin had disappeared, she promptly asked Jeserac what had happened to him. Jeserac, with only a momentary hesitation, told her. If Alvin did not want company, the answer was in his own hands. His tutor neither approved nor disapproved of this relationship. On the whole, he rather liked Alystra and hoped that her influence would help Alvin to adjust himself to life in Diaspar.

The fact that Alvin was spending his time at Council Hall could only mean that he was engaged on some research project, and this knowledge at least served to quell any suspicions Alystra might have concerning possible rivals. But though her jealousy was not aroused, her curiosity was. She sometimes reproached herself for abandoning Alvin in the Tower of Loranne, though she knew that if the circumstances were repeated she would do exactly the same thing again. There was no way of understanding Alvin's mind, she told herself, unless she could discover what he was trying to do.

She walked purposefully into the main hall, impressed but not overawed by the hush that fell as soon as she passed through the entrance. The information machines were ranged side by side against the far wall, and she chose one at random.

As soon as the recognition signal lighted up, she said, "I am looking for Alvin; he is somewhere in this building. Where can I find him?"

Even after a lifetime, one never grew wholly accustomed to the complete absence of time lag when an information machine replied to an ordinary question. There were people who knew---or claimed to know---how it was done, and talked learnedly of "access time" and "storage space" but that made the final result none the less marvellous. Any question of a purely factual nature, within the city's truly enormous range of available information, could be answered immediately. Only if complex calculations were involved before a reply could be given would there be any appreciable delay.

"He is with the monitors," came the reply. It was not very helpful, since the name conveyed nothing to Alystra. No machine ever volunteered more information than it was asked for, and learning to frame questions properly was an art which often took a long time to acquire.

"How do I reach him?" asked Alystra. She would find what the monitors were when she got to them.

"I cannot tell you unless you have the permission of the Council."

This was a most unexpected, even a disconcerting, development. There were very few places in Diaspar that could not be visited by anyone who pleased. Alystra was quite certain that Alvin had not obtained Council permission, and this could only mean that a higher authority was helping him.

The Council ruled Diaspar, but the Council itself could be overridden by a superior power---the all-but-infinite intellect of the Central Computer. It was difficult not to think of the Central Computer as a living entity, localized in a single spot, though actually it was the sum total of all the machines in Diaspar. Even if it was not alive in the biological sense, it certainly possessed at least as much awareness and self-consciousness as a human being. It must know what Alvin was doing, and, therefore, it must approve, otherwise it would have stopped him or referred him to the Council, as the information machine had done to Alystra.

There was no point in staying here. Alystra knew that any attempt to find Alvin---even if she knew exactly where he was in this enormous building---would be doomed to failure. Doors would fail to open; slideways would reverse when she stood on them, carrying her backward instead of forward; elevator fields would be mysteriously inert, refusing to lift her from one floor to another. If she persisted, she would be gently conveyed out into the street by a polite but firm robot, or else shuttled round and round Council Hall until she grew fed up and left under her own volition.

She was in a bad temper as she walked out into the street. She was also more than a little puzzled, and for the first time felt that there was some mystery here which made her personal desires and interests seem very trivial indeed. That did not mean that they would be any the less important to her. She had no idea what she was going to do next, but she was sure of one thing. Alvin was not the only person in Diaspar who could be stubborn and persistent.

JESERAC sat motionless within a whirlpool of numbers. The first thousand primes, expressed in the binary scale that had been used for all arithmetical operations since electronic computers were invented, marched in order before him. Endless ranks of 1's and 0's paraded past, bringing before Jeserac's eyes the complete sequence of all those numbers that possessed no factors except themselves and unity. There was a mystery about the primes that had always fascinated Man, and they held his imagination still.

Jeserac was no mathematician, though sometimes he liked to believe he was. All he could do was to search among the infinite array of primes for special relationships and rules which more talented men might incorporate in general laws. He could find how numbers behaved, but he could not explain why. It was his pleasure to hack his way through the arithmetical jungle, and sometimes he discovered wonders that more skillful explorers had missed.

He set up the matrix of all possible integers, and started his computer stringing the primes across its surface as beads might be arranged at the intersections of a mesh. Jeserac had done this a hundred times before, and it had never taught him anything. But he was fascinated by the way in which the numbers he was studying were scattered, apparently according to no laws, across the spectrum of the integers. He knew the laws of distribution that had already been discovered, but always hoped to discover more.

He could scarcely complain about the interruption. If he had wished to remain undisturbed, he should have set his annunciator accordingly. As the gentle chime sounded in his ear, the wall of numbers shivered, the digits blurred together, and Jeserac returned to the world of mere reality.

He recognized Khedron at once, and was none too pleased. Jeserac did not care to be disturbed from his ordered way of life, and Khedron represented the unpredictable. However, he greeted his visitor politely enough and concealed all trace of his mild concern.

When two people met for the first time in Diaspar---or even for the hundredth---it was customary to spend an hour or so in an exchange of courtesies before getting down to business, if any. Khedron somewhat offended Jeserac by racing through these formalities in a mere fifteen minutes and then saying abruptly: "I'd like to talk to you about Alvin. You're his tutor, I believe."

"That is true," replied Jeserac. "I still see him several times a week---as often as he wishes."

"And would you say that he was an apt pupil?"

Jeserac thought that over; it was a difficult question to answer. The pupil-tutor relationship was extremely important and was, indeed, one of the foundations of life in Diaspar. On the average, ten thousand new minds came into the city every year. Their previous memories were still latent, and for the first twenty years of their existence everything around them was fresh and strange. They had to be taught to use the myriad machines and devices that were the background of everyday life, and they had to learn their way through the most complex society Man had ever built.

Part of this instruction came from the couples chosen to be the parents of the new citizens. The selection was by lot, and the duties were not onerous. Eriston and Etania had devoted no more than a third of their time to Alvin's upbringing, and they had done all that was expected of them.

Jeserac's duties were confined to the more formal aspects of Alvin's education; it was assumed that his parents would teach him how to behave in society and introduce him to an ever-widening circle of friends. They were responsible for Alvin's character, Jeserac for his mind.

"I find it rather hard to answer your question," Jeserac replied. "Certainly there is nothing wrong with Alvin's intelligence, but many of the things that should concern him seem to be a matter of complete indifference. On the other hand, he shows a morbid curiosity regarding subjects which we do not generally discuss."

"The world outside Diaspar, for example?"

"Yes---but how did you know?"

Khedron hesitated for a moment, wondering how far he should take Jeserac into his confidence. He knew that Jeserac was kindly and well-intentioned, but he knew also that he must be bound by the same taboos that controlled everyone in Diaspar---everyone except Alvin.

"I guessed it," he said at last.

Jeserac settled down more comfortably in the depths of the chair he had just materialized. This was an interesting situation, and he wanted to analyze it as fully as possible. There was not much he could learn, however, unless Khedron was willing to co-operate.

He should have anticipated that Alvin would one day meet the Jester, with unpredictable consequences. Khedron was the only other person in the city who could be called eccentric---and even his eccentricity had been planned by the designers of Diaspar. Long ago it had been discovered that without some crime or disorder, Utopia soon became unbearably dull. Crime, however, from the nature of things, could not be guaranteed to remain at the optimum level which the social equation demanded. If it was licenced and regulated, it ceased to be crime.

The office of Jester was the solution---at first sight naive, yet actually profoundly subtle---which the city's designers had evolved. In all the history of Diaspar there were less than two hundred persons whose mental inheritance fitted them for this peculiar role. They had certain privileges that protected them from the consequences of their actions, though there had been Jesters who had overstepped the mark and paid the only penalty that Diaspar could impose---that of being banished into the future before their current incarnation had ended.

On rare and unforeseeable occasions, the Jester would turn the city upside-down by some prank which might be no more than an elaborate practical joke, or which might be a calculated assault on some currently cherished belief or way of life. All things considered, the name "Jester" was a highly appropriate one. There had once been men with very similar duties, operating with the same licence, in the days when there were courts and kings.

"It will help," said Jeserac, "if we are frank with one another. We both know that Alvin is a Unique---that he has never experienced any earlier life in Diaspar. Perhaps you can guess, better than I can, the implications of that. I doubt if anything that happens in the city is totally unplanned, so there must be a purpose in his creation. Whether he will achieve that purpose---whatever it is---I do not know. Nor do I know whether it is good or bad. I cannot guess what it is."

"Suppose it concerns something external to the city?"

Jeserac smiled patiently; the Jester was having his little joke, as was only to be expected.

"I have told him what lies there; he knows that there is nothing outside Diaspar except the desert. Take him there if you can; perhaps you know a way. When he sees the reality, it may cure the strangeness in his mind."

"I think he has already seen it," said Khedron softly. But he said it to himself, and not to Jeserac.

"I do not believe that Alvin is happy," Jeserac continued. "He has formed no real attachments, and it is hard to see how he can while he still suffers from this obsession. But after all, he is very young. He may grow out of this phase, and become part of the pattern of the city."

Jeserac was talking to reassure himself; Khedron wondered if he really believed what he was saying.

"Tell me, Jeserac," asked Khedron abruptly, "does Alvin know that he is not the first Unique?"

Jeserac looked startled, then a little defiant.

"I might have guessed," he said ruefully, "that you would know that. How many Uniques have there been in the whole history of Diaspar? As many as ten?"

"Fourteen," answered Khedron without hesitation. "Not counting Alvin."

"You have better information than I can command," said Jeserac wryly. "Perhaps you can tell me what happened to those Uniques?"

"They disappeared."

"Thank you: I knew that already. That is why I have told Alvin as little as possible about his predecessors: it would hardly help him in his present mood. Can I rely on your co-operation?"

"For the moment---yes. I want to study him myself; mysteries have always intrigued me, and there are too few in Diaspar. Besides, I think that Fate may be arranging a jest beside which all my efforts will look very modest indeed. In that case, I want to make sure that I am present at its climax."

"You are rather too fond of talking in riddles," complained Jeserac. "Exactly what are you anticipating?"

"I doubt if my guesses will be any better than yours. But I believe this---neither you nor I nor anyone in Diaspar will be able to stop Alvin when he has decided what he wants to do. We have a very interesting few centuries ahead of us."

Jeserac sat motionless for a long time, his mathematics forgotten, after the image of Khedron had faded from sight. A sense of foreboding, the like of which he had never known before, hung heavily upon him. For a fleeting moment he wondered if he should request an audience with the Council---but would that not be making a ridiculous fuss about nothing? Perhaps the whole affair was some complicated and obscure jest of Khedron's, though he could not imagine why he had been chosen to be its butt.

He thought the matter over carefully, examining the problem from every angle. After little more than an hour, he made a characteristic decision.

He would wait and see.

+++

Alvin wasted no time learning all that he could about Khedron. Jeserac, as usual, was his main source of information. The old tutor gave a carefully factual account of his meeting with the Jester, and added what little he knew about the other's mode of life. Insofar as such a thing was possible in Diaspar, Khedron was a recluse: no one knew where he lived or anything about his way of life. The last jest he had contrived had been a rather childish prank involving a general paralysis of the moving ways. That had been fifty years ago: a century earlier he had let loose a particularly revolting dragon which had wandered around the city eating every existing specimen of the works of the currently most popular sculptor. The artist himself, justifiably alarmed when the beast's single-minded diet became obvious, had gone into hiding and not emerged until the monster had vanished as mysteriously as it had appeared.

One thing was obvious from these accounts. Khedron must have a profound understanding ot the machines and powers that ruled the city, and could make them obey his will in ways which no one else could do. Presumably there must be some overriding control which prevented any too-ambitious Jester from causing permanent and irreparable damage to the complex structure of Diaspar.

Alvin filed all this information away, but made no move to contact Khedron. Though he had many questions to ask the Jester, his stubborn streak of independence---perhaps the most truly unique of all his qualities---made him determined to discover all he could by his own unaided efforts. He had embarked on a project that might keep him busy for years, but as long as he felt that he was moving toward his goal he was happy.

Like some traveller of old mapping out an unknown land, he had begun the systematic exploration of Diaspar. He spent his weeks and days prowling through the lonely towers at the margin of the city, in the hope that somewhere he might discover a way out into the world beyond. During the course of his search he found a dozen of the great air vents opening high above the desert, but they were all barred---and even if the bars had not been there, the sheer drop of almost a mile was sufficient obstacle.

He found no other exits, though he explored a thousand corridors and ten thousand empty chambers. All these buildings were in that perfect and spotless condition which the people of Diaspar took for granted as part of the normal order of things. Sometimes Alvin would meet a wandering robot, obviously on a tour of inspection, and he never failed to question the machine. He learned nothing, because the machines he encountered were not keyed to respond to human speech or thoughts. Though they were aware of his presence, for they floated politely aside to let him pass, they refused to engage in conversation.

There were times when Alvin did not see another human being for days. When he felt hungry, he would go into one of the living apartments and order a meal. Miraculous machines to whose existence he seldom gave a thought would wake to life after aeons of slumber. The patterns they had stored in their memories would flicker on the edge of reality, organizing and directing the matter they controlled. And so a meal prepared by a master chef a hundred million years before would be called again into existence to delight the palate or merely to satisfy the appetite.

The loneliness of this deserted world---the empty shell surrounding the living heart of the city---did not depress Alvin. He was used to loneliness, even when he was among those he called his friends. This ardent exploration, absorbing all his energy and interest, made him forget for the moment the mystery of his heritage and the anomaly that cut him off from all his fellows.

He had explored less than one-hundredth of the city's rim when he decided that he was wasting his time. His decision was not the result of impatience, but of sheer common sense. If need be, he was prepared to come back and finish the task, even if it took him the remainder of his life. He had seen enough, however, to convince him that if a way out of Diaspar did exist, it would not be found as easily as this. He might waste centuries in fruitless search unless he called upon the assistance of wiser men.

Jeserac had told him flatly that he knew no road out of Diaspar, and doubted if one existed. The information machines, when Alvin had questioned them, had searched their almost infinite memories in vain. They could tell him every detail of the city's history back to the beginning of recorded time---back to the barrier beyond which the Dawn Ages lay forever hidden. But they could not answer Alvin's simple question, or else some higher power had forbidden them to do so.

He would have to see Khedron again.

IN his short lifetime, Alvin had met less than one-thousandth of the inhabitants of Diaspar. He was not surprised, therefore, that the man confronting him was a stranger. What did surprise him was to meet anyone at all here in this deserted tower, so near the frontier of the unknown.

He turned his back on the mirror world and faced the intruder. Before he could speak, the other had addressed him.

"You are Alvin, I believe. When I discovered that someone was coming here, I should have guessed it was you."

The remark was obviously not intended to give offence; it was a simple statement of fact, and Alvin accepted it as such. He was not surprised to be recognized; whether he liked it or not, the fact of his uniqueness, and its unrevealed potentialities, had made him known to everyone in the city.

"I am Khedron," continued the stranger, as if that explained everything. "They call me the Jester."

Alvin looked blank, and Khedron shrugged his shoulders in mock resignation.

"Ah, such is fame! Still, you are young and there have been no jests in your lifetime. Your ignorance is excused."

There was something refreshingly unusual about Khedron. Alvin searched his mind for the meaning of the strange word "Jester"; it evoked the faintest of memories, but he could not identify it. There were many such titles in the complex social structure of the city, and it took a lifetime to learn them all.

"Do you often come here?" Alvin asked, a little jealously. He had grown to regard the Tower of Loranne as his personal property and felt slightly annoyed that its marvels were known to anyone else. But had Khedron, he wondered, ever looked out across the desert or seen the stars sinking down into the west?

"No," said Khedron, almost as if answering his unspoken thoughts. "I have never been here before. But it is my pleasure to learn of unusual happenings in the city and it is a very long time since anyone went to the Tower of Loranne."

Alvin wondered fleetingly how Khedron knew of his earlier visits, but quickly dismissed the matter from his mind. Diaspar was full of eyes and ears and other more subtle sense organs which kept the city aware of all that was happening within it. Anyone who was sufficiently interested could no doubt find a way of tapping these channels.

"Even if it is unusual for anyone to come here," said Alvin, still fencing verbally, "why should you be interested?"

"Because in Diaspar," replied Khedron, "the unusual is my prerogative. I had marked you down a long time ago; I knew we should meet some day. After my fashion, I too am unique. Oh, not in the way that you are; this is not my first life. I have walked a thousand times out of the Hall of Creation. But somewhere back at the beginning I was chosen to be Jester, and there is only one Jester at a time in Diaspar. Most people think that is one too many."

There was an irony about Khedron's speech that left Alvin still floundering. It was not the best of manners to ask direct personal questions, but after all Khedron had raised the subject.

"I'm sorry about my ignorance," said Alvin. "But what is a Jester, and what does he do?"

"You ask 'what,' " replied Khedron, "so I'll start by telling you 'why' It's a long story, but I think you will be interested."

"I am interested in everything," said Alvin, truthfully enough.

"Very well. The men---if they were men, which I sometimes doubt---who designed Diaspar had to solve an incredibly complex problem. Diaspar is not merely a machine, you know---it is a living organism, and an immortal one. We are so accustomed to our society that we can't appreciate how strange it would have seemed to our first ancestors. Here we have a tiny, closed world which never changes except in its minor details, and yet which is perfectly stable, age after age. It has probably lasted longer than the rest of human history---yet in that history there were, so it is believed, countless thousands of separate cultures and civilizations which endured for a little while and then perished. How did Diaspar achieve its extraordinary stability?"

Alvin was surprised that anyone should ask so elementary a question, and his hopes of learning something new began to wane.

"Through the Memory Banks, of course," he replied. "Diaspar is always composed of the same people, though their actual groupings change as their bodies are created or destroyed."

Khedron shook his head.

"That is only a very small part of the answer. With exactly the same people, you could build many different patterns of society. I can't prove that, and I've no direct evidence of it, but I believe it's true. The designers of the city did not merely fix its population; they fixed the laws governing its behaviour. We're scarcely aware that those laws exist, but we obey them. Diaspar is a frozen culture, which cannot change outside of narrow limits. The Memory Banks store many other things outside the patterns of our bodies and personalities. They store the image of the city itself, holding its every atom rigid against all the changes that time can bring. Look at this pavement---it was laid down millions of years ago, and countless feet have walked upon it. Can you see any sign of wear? Unprotected matter, however adamant, would have been ground to dust ages ago. But as long as there is power to operate the Memory Banks, and as long as the matrices they contain can still control the patterns of the city, the physical structure of Diaspar will never change."

"But there have been some changes," protested Alvin. "Many buildings have been torn down since the city was built, and new ones erected."

"Of course---but only by discharging the information stored in the Memory Banks and then setting up new patterns. In any case, I was merely mentioning that as an example of the way the city preserves itself physically. The point I want to make is that in the same way there are machines in Diaspar that preserve our social structure. They watch for any changes, and correct them before they become too great. How do they do it? I don't know---perhaps by selecting those who emerge from the Hall of Creation. Perhaps by tampering with our personality patterns; we may think we have free will, but can we be certain of that?

"In any event, the problem was solved. Diaspar has survived and come safely down the ages, like a great ship carrying as its cargo all that is left of the human race. It is a tremendous achievement in social engineering, though whether it is worth doing is quite another matter.

"Stability, however, is not enough. It leads too easily to stagnation, and thence to decadence. The designers of the city took elaborate steps to avoid this, though these deserted buildings suggest that they did not entirely succeed. I, Khedron the Jester, am part of that plan. A very small part, perhaps. I like to think otherwise, but I can never be sure."

"And just what is that part?" asked Alvin, still very much in the dark, and becoming a little exasperated.

"Let us say that I introduce calculated amounts of disorder into the city. To explain my operations would be to destroy their effectiveness. Judge me by my deeds, though they are few, rather than my words, though they are many."

Alvin had never before met anyone quite like Khedron. The Jester was a real personality---a character who stood head and shoulders above the general level of uniformity which was typical of Diaspar. Though there seemed no hope of discovering precisely what his duties were and how he carried them out, that was of minor importance. All that mattered, Alvin sensed, was that here was someone to whom he could talk---when there was a gap in the monologue---and who might give him answers to many of the problems that had puzzled him for so long.

They went back together down through the corridors of the Tower of Loranne, and emerged beside the deserted moving way. Not until they were once more in the streets did it occur to Alvin that Khedron had never asked him what he had been doing out here at the edge of the unknown. He suspected that Khedron knew, and was interested but not surprised. Something told him that it would be very difficult to surprise Khedron.

They exchanged index numbers, so that they could call each other whenever they wished. Alvin was anxious to see more of the Jester, though he fancied that his company might prove exhausting if it was too prolonged. Before they met again, however, he wanted to find what his friends, and particularly Jeserac, could tell him about Khedron.

"Until our next meeting," said Khedron, and promptly vanished. Alvin was somewhat annoyed. If you met anyone when you were merely projecting yourself, and were not present in the flesh, it was good manners to make that clear from the beginning. It could sometimes put the party who was ignorant of the facts at a considerable disadvantage. Probably Khedron had been quietly at home all the time---wherever his home might be. The number that he had given Alvin would insure that any messages would reach him, but did not reveal where he lived. That at lest was according to normal custom. You might be free enough with index numbers, but your actual address was something you disclosed only to vour intimate friends.

As he made his wav back into the city, Alvin pondered over all that Khedron had told him about Diaspar and its social organization. It was strange that he had met no one else who had ever seemed dissatisfied with their mode of life. Diaspar and its inhabitants had been designed as part of one master plan; they formed a perfect symbiosis. Throughout their long lives, the people of the city were never bored. Though their world might be a tiny one by the standard or earlier ages, its complexity was overwhelming, its wealth of wonder and treasure beyond calculation. Here Man had gathered all the fruits of his genius, everything that had been saved from the ruin of the past. All the cities that had ever been, so it was said, had given something to Diaspar; before the coming of the Invaders, its name had been known on all the worlds that Man had lost. Into the building of Diaspar had gone all the skill, all the artistry of the Empire. When the great days were coming to an end, men of genius had remoulded the city and given it the machines that made it immortal. Whatever might be forgotten, Diaspar would live and bear the descendants of Man safely down the stream of time.

They had achieved nothing except survival, and were content with that. There were a million things to occupy their lives between the hour when they came, almost full-grown, from the Hall of Creation and the hour when, their bodies scarcely older, they returned to the Memory Banks of the city. In a world where all men and women possess an intelligence that would once have been the mark of genius, there can be no danger of boredom. The delights of conversation and argument---the intricate formalities of social intercourse---these alone were enough to occupy a goodly portion of a lifetime. Beyond those were the great formal debates, when the whole city would listen entranced while its keenest minds met in combat or strove to scale those mountain peaks of philosophy which are never conquered yet whose challenge never palls.

No man or woman was without some absorbing intellectual interest. Eriston, for example, spent much of his time in prolonged soliloquies with the Central Computer, which virtually ran the city, yet which had leisure for scores of simultaneous discussions with anyone who cared to match his wits against it. For three hundred years, Eriston had been trying to construct logical paradoxes which the machine could not resolve. He did not expect to make serious progress before he had used up several lifetimes.

Etania's interests were of a more aesthetic nature. She designed and constructed, with the aid of the matter organizers, three-dimensional interlacing patterns of such beautiful complexity that they were really extremely advanced problems in topology. Her work could be seen all over Diaspar, and some of her patterns had been incorporated in the floors of the great halls of choreography, where they were used as the basis for evolving new ballet creations and dance motifs.

Such occupations might have seemed arid to those who did not possess the intellect to appreciate their subtleties. Yet there was no one in Diaspar who could not understand something of what Eriston and Etania were trying to do and did not have some equally consuming interest of his own.

Athletics and various sports, including many only rendered possible by the control of gravity, made pleasant the first few centuries of youth. For adventure and the exercise of the imagination, the sagas provided all that anyone could desire. They were the inevitable end product of that striving for realism which began when men started to reproduce moving images and to record sounds, and then to use these techniques to enact scenes from real or imaginary life. In the sagas, the illusion was perfect because all the sense impressions involved were fed directly into the mind and any conflicting sensations were diverted. The entranced spectator was cut off from reality as long as the adventure lasted; it was as if he lived a dream yet believed he was awake.

In a world of order and stability, which in its broad outlines had not changed for a billion years, it was perhaps not surprising to find an absorbing interest in games of chance. Humanity had always been fascinated by the mystery of the falling dice, the turn of a card, the spin of the pointer. At its lowest level, this interest was based on mere cupidity---and that was an emotion that could have no place in a world where everyone possessed all that they could reasonably need. Even when this motive was ruled out, however, the purely intellectual fascination of chance remained to seduce the most sophisticated minds. Machines that behaved in a purely random way---events whose outcome could never be predicted, no matter how much information one had---from these philosopher and gambler could derive equal enjoyment.

And there still remained, for all men to share, the linked worlds of love and art. Linked, because love without art is merely the slaking of desire, and art cannot be enjoyed unless it is approached with love.

Men had sought beauty in many forms---in sequences of sound, in lines upon paper, in surfaces of stone, in the movements of the human body, in colours ranged through space. All these media still survived in Diaspar, and down the ages others had been added to them. No one was yet certain if all the possibilities of art had been discovered; or if it had any meaning outside the mind of man.

And the same was true of love.