Jan Rodricks was coming home, six months older, to the world he had left eighty years before.

The ship of the Overlords came sliding in along its glowing meteor-trail through the heart of Carina. It had begun its mad deceleration among the outer planets, but even while passing Mars it had still possessed an appreciable fraction of the velocity of light. Slowly the immense fields surrounding the Sun were absorbing its momentum, while for a million kilometres behind, the stray energies of the stardrive were painting the heavens with fire.

This time he was no longer a stowaway, hidden in a secret chamber. He stood behind the three pilots (why, he wondered, did they need so many?) watching the patterns come and go on the great screen that dominated the control room. The colours and shapes it showed were meaningless to him: he assumed that they were conveying information which in a vessel designed by men would have been displayed on banks of meters. But sometimes the screen showed the surrounding star-fields, and soon, he hoped, it would be showing Earth.

He was glad to be home, despite the effort he had devoted to escaping from it. In these few months he had grown up. He had seen so much, travelled so far, and now was weary for his own familiar world. He understood, now, why the Overlords had sealed Earth from the stars. Humanity still had very far to go before it could play any part in the civilization he had glimpsed.

It might be -- though this he refused to accept -- that mankind could never be more than an inferior species, preserved in an out-of-the-way zoo with the Overlords as keepers. Perhaps that was what Vindarten had meant when he gave Jan that ambiguous warning, just before his departure. "Much may have happened," the Overlord had said, "in the time that has passed on your planet. You may not know your world when you see it again."

Perhaps not, thought Jan: eighty years was a long time, and though he was young and adaptable, he might find it hard to understand all the changes that had come to pass. But of one thing he was certain -- men would want to hear his story, and to know what he had glimpsed of the civilization of the Overlords.

They had treated him well, as he had assumed they would. Of the outward journey he had known nothing: when the injection had worn off and he had emerged, the ship was already entering the Overlord system. He had climbed out of his fantastic hiding-place, and found to his relief that the oxygen set was not needed. The air was thick and heavy, but he could breathe without difficulty. He had found himself in the ship's enormous red-lit hold, among countless other packing-cases and all the impedimenta one would expect on a liner of space or of sea. It had taken him almost an hour to find his way to the control room and to introduce himself to the crew.

Their lack of surprise had puzzled him: he knew that the Overlords showed few emotions, but he had expected some reaction. Instead, they simply continued with their work, watching the great screen and playing with the countless keys on their control panels. It was then that he knew that they were landing, for from time to time the image of a planet -- larger at each appearance -- would flash upon the screen.

And then, in unison, the three Overlords had risen from their seats, and he knew that the voyage was over. They did not speak to their passenger or to each other, and when one of them beckoned to him to follow, Jan realized something that he should have thought of before. There might well be no one here, at this end of Karellen's enormously long supply line, who understood a word of English.

They watched him gravely as the great doors opened before his eager eyes. This was the supreme moment of his life: now he was to be the first human being ever to look upon a world lit by another sun. The ruby light of NGS 549672 came flooding into the ship, and there before him lay the planet of the Overlords.

What had he expected? He was not sure. Vast buildings, cities whose towers were lost among the clouds, machines beyond imagination -- these would not have surprised him. Yet what he saw was an almost featureless plain, reaching out to an unnaturally close horizon, and broken only by three more of the Overlords' ships, a few kilometres away.

Yet there was never the slightest sense of motion or acceleration -- only a perfectly constant gravity, which he judged to be about a fifth of Earth's. The immense forces that drove the ship must have been compensated with exquisite precision.

For a moment Jan felt a surge of disappointment. Then he shrugged his shoulders, realizing that, after all, one would expect to find a space-port in some such remote and uninhabited region as this.

It was cold, though not uncomfortably so. The light from the great red sun low down on the horizon was quite ample for human eyes, but Jan wondered how long it would be before he yearned for greens and blues. Then he saw that enormous, wafer-thin crescent reaching up the sky like a great bow placed beside the sun. He stared at it for a long time before he realized that his journey was not yet altogether ended. That was the world of the Overlords. This must be its satellite, merely the base from which their vessels operated.

They had taken him across in a ship no larger than a terrestrial airliner. Feeling a pygmy, he had climbed up into one of the great seats to try and see something of the approaching planet through the observation windows.

The journey was so swift that he had time to make out few details on the expanding globe beneath. Even so near to home, it seemed, the Overlords used some version of the stardrive, for in a matter of minutes they were falling down through a deep, cloud-flecked atmosphere. When the doors opened, they stepped out into a vaulted chamber with a roof that must have swung swiftly shut behind them, for there was no sign of any entrance overhead.

There was no way he could get out of the building, because the great doors had no visible controls. When an Overlord walked up to them, they simply opened. Jan had tried the same trick, had waved objects high in the air to interrupt any controlling light-beam, had tried everything he could imagine -- with no result at all. He realized that a man from the Stone Age, lost in a modern city building, might be equally helpless. Once he had tried to walk out when one of the Overlords left, but had been gently shooed back. As he was very anxious not to annoy his hosts, he did not persist.

It would be more than frustrating, thought Jan, if the only Overlords who spoke his language were all back on Earth. He could only wait and hope for the best. Surely some scientist, some expert on alien races, would come and take charge of him! Or was he so unimportant that no one could be bothered?

It was two days before Jan left this building. He was an unexpected consignment, and they had nowhere to put him. To make matters worse, not one of the Overlords could understand English. Communication was practically impossible, and Jan realized bitterly that getting in touch with an alien race was not so easy as it was so often depicted in fiction. Sign language proved singularly unsuccessful, for it depended too much on a body of gestures, expressions and attitudes which the Overlords and mankind did not possess in common.

Once Vindarten had taken charge of him, Jan had no more worries. He also had no opportunity of doing the things he wished, for almost all his time was spent meeting Overlord scientists anxious to carry out obscure tests with complicated instruments. Jan was very wary of these machines, and after one session with some kind of hypnotic device had a splitting headache for several hours. He was perfectly willing to cooperate, but was not sure if his investigators realized his limitations, both mental and physical. It was certainly a long time before he could convince them that he had to sleep at regular intervals.

Vindarten arrived before Jan had begun to get desperate. The Overlord spoke very bad English, much too rapidly, but improved with amazing speed. In a few days they were able to talk together with little trouble on any subject that did not demand a specialized vocabulary.

Between these investigations, he caught momentary glimpses of the city, and realized how difficult -- and dangerous -- it would be for him to travel around in it. Streets were practically non-existent, and there seemed to be no surface transport. This was the home of creatures who could fly, and who had no fear of gravity. It was nothing to come without warning upon a vertiginous drop of several hundred metres, or to find that the only entrance into a room was an opening high up in the wall. In a hundred ways, Jan began to realize that the psychology of a race with wings must be fundamentally different from that of earthbound creatures.

The architecture of the Overlords was bleakly functional: Jan saw no ornaments, nothing that did not serve a purpose, even though that purpose was often beyond his understanding. If a man from mediaeval times could have seen this red-lit city, and the beings moving through it, he would certainly have believed himself in Hell. Even Jan, for all his curiosity and scientific detachment, sometimes found himself on the verge of unreasoning terror. The absence of a single familiar reference point can be utterly unnerving even to the coolest and clearest minds.

It was strange to see the Overlords flying like great birds among the towers of their city, their pinions moving with slow, powerful beats. And there was a scientific problem here. This was a large planet -- larger than Earth. Yet its gravity was low, and Jan wondered why it had so dense an atmosphere. He questioned Vindarten on this, and discovered, as he had half expected, that this was not the original planet of the Overlords. They had evolved on a much smaller world and then conquered this one, changing not only its atmosphere but even its gravity.

Jan also sensed that the world of the Overlords was full of sounds that he could not hear. Occasionally he caught complex rhythmical patterns racing up and down through the audible spectrum, to vanish at the upper or lower edge of hearing. Vindarten did not seem to understand what Jan meant by music, so he was never able to solve this problem to his satisfaction.

The city was not very large: it was certainly far smaller then London or New York had been at their heyday. According to Vindarten, there were several thousand such cities scattered over the planet, each one designed for some specific purpose. On Earth, the closest parallel to this place would have been a university town -- except that the degree of specialization had gone much further. This entire city was devoted, Jan soon discovered, to the study of alien cultures.

And there was much he did not understand, and which Vindarten could or would not attempt to explain. What were those flashing lights and changing shapes, the things that flickered through the air so swiftly that he could never be certain of their existence? They could have been something tremendous and awe-inspiring -- or as spectacular yet trivial as the neon signs of old-time Broadway.

In one of their first trips outside the bare cell in which Jan lived, Vindarten had taken him to the museum. It had given Jan a much needed psychological boost to find himself in a place whose purpose he could fully understand. Apart from the scale upon which it was built, this museum might well have been on Earth. They had taken a long time to reach it, falling steadily on a great platform that moved like a piston in a vertical cylinder of unknown length. There were no visible controls, and the sense of acceleration at the beginning and ending of the descent was quite noticeable. Presumably the Overlords did not waste their compensating field devices for domestic uses. Jan wondered if the whole interior of this world was riddled with excavations: and why had they limited the size of the city, going underground instead of outwards? That was just another of the enigmas he never solved.

One could have spent a lifetime exploring these colossal chambers. Here was the loot of planets, the achievements of more civilizations than Jan could guess. But there was no time to see much. Vindarten placed him carefully on a strip of flooring that at first sight seemed an ornamental pattern. Then Jan remembered that there were no ornaments here -- and at the same time, something invisible grasped him gently and hurried him forward. He was moving past the great display cases, past vistas of unimaginable worlds, at a speed of twenty or thirty kilometres an hour.

They must have travelled several kilometres before Jan's guide grasped him again, and with a surge of his great wings lifted him away from whatever force was propelling them. Before them stretched a huge, half-empty hail, flooded with a familiar light that Jan had not seen since leaving Earth. It was faint, so that it would not pain the sensitive eyes of the Overlords, but it was, unmistakably, sunlight. Jan would never have believed that anything so simple or so commonplace could have evoked such yearning in his heart.

So this was the exhibit for Earth. They walked for a few metres past a beautiful model of Paris, past art-treasures from a dozen centuries grouped incongruously together, past modem calculating machines and paleolithic axes, past television receivers and Hero of Alexandra's steam-turbine. A great doorway opened ahead of them, and they were in the office of the Curator for Earth.

Was he seeing a human being for the first time? Jan wondered. Had he ever been to Earth, or was it just another of the many planets in his charge, of whose exact location he was not precisely sure? Certainly he neither spoke nor understood English, and Vindarten had to act as interpreter.

The Overlords had solved the problem of museum fatigue. There was no need for anyone to walk.

Jan had spent several hours here, talking into a recording device while the Overlords presented various terrestrial objects to him. Many of these, he discovered to his shame, he could not identify. His ignorance of his own race and its achievements was enormous: he wondered if the Overlords, for all their superb mental gifts, could really grasp the complete pattern of human culture.

Vindarten took him out of the museum by a different route. Once again they floated effortlessly through great vaulted corridors, but this time they were moving past the creations of nature, not of conscious mind. Sullivan, thought Jan, would have given his life to be here, to see what wonders evolution had wrought on a hundred worlds. But Sullivan, he remembered, was probably already dead.

Then, without any warning, they were on a galley high above a large circular chamber, perhaps a hundred metres across. As usual, there was no protective parapet, and for a moment Jan hesitated to go near the edge. But Vindarten was standing on the very brink, looking calmly downwards, so Jan moved cautiously forward to join him.

"Why did you make that noise?" asked Vindarten.

It was lifeless, of course -- not, as he had thought in that first moment of panic, consciously staring up at him. It filled almost all that great circular space, and the ruby light gleamed and shifted in its crystal depths. It was a single giant eye.

"But why? Surely you did not imagine that there could be any danger here?"

The floor was only twenty metres below -- far, far too close. Afterwards, Jan was sure that his guide had not intended to surprise him, and was completely taken aback by his reaction. For he had given one tremendous yell and jumped backwards from the gallery's edge, in an involuntary effort to hide what lay below. It was not until the muffled echoes of his shout had died away in the thick atmosphere that he steeled himself to go forward again.

"Anything completely unexpected is frightening. Until a novel situation is analyzed, it is safest to assume the worst."

"I was frightened," Jan confessed sheepishly.

Jan wondered if he could explain what a reflex action was, but decided not to attempt it.

Vindarten could tell him little: this was not his field of knowledge, and he was not particularly curious. From the Overlord's description, Jan built up a picture of a cyclopean beast living among the asteroidal rubble of some distant sun, its growth uninhibited by gravity, depending for food and life upon the range and resolving power of its single eye.

His heart was still pounding violently as he stared down once more at that monstrous eye. Of course, it might have been a model, enormously enlarged as were microbes and insects in terrestrial museums. Yet even as he asked the question, Jan knew, with a sickening certainty, that it was no larger than life.

There seemed no limit to what Nature could do if she was pressed, and Jan felt an irrational pleasure at discovering something which the Overlords would not attempt. They had brought a full-sized whale from Earth -- but they had drawn the line at this.

And there was the time when he had gone up, endlessly up, until the walls of the elevator had faded through opalescence into a crystal transparency. He was standing, it seemed, unsupported among the uppermost peaks of the city, with nothing to protect him from the abyss. But he felt no more vertigo than one does in an aeroplane, for there was no sense of contact with the distant ground. He was above the clouds, sharing the sky with a few pinnacles of metal or stone. A rose-red sea, the cloud-layer rolled sluggishly beneath him. There were two pale and tiny moons in the sky, not far from the sombre sun. Near the centre of that bloated red disc was a small, dark shadow, perfectly circular. It might have been a sunspot, or another moon in transit.

And then, slowly, the mountain began to change. When he saw it first, it was a dull and almost sinister red, with a few faint markings near its crown that he could not clearly distinguish. He was trying to focus on them when he realized that they were moving…

When he had turned half-circle he saw the mountain. It was not on the horizon, but beyond it -- a single serrated peak, climbing up over the edge of the world, its lower slopes hidden as the bulk of an iceberg is concealed below the water-line. He tried to guess its size, and failed completely. Even on a world with gravity as low as this, it seemed hard to believe that such mountains could exist. Did the Overlords, he wondered, sport themselves upon its slopes and sweep like eagles around those immense buttresses?

Jan slowly moved his gaze along the horizon. The cloud-cover extended clear to the edge of this enormous world, but in one direction, at an unguessable distance, there was a mottled patch that might have marked the towers of another city. He stared at it for a long while, then continued his careful survey.

At first he could not believe his eyes. Then he forced himself to remember that all his preconceived ideas were worthless here: he must not let his mind reject any message his senses brought into the hidden chamber of the brain. He must not try to understand -- only to observe. Understanding would come later, or not at all.

The mountain -- he still thought of it as such, for there was no other word that could serve -- seemed to be alive. He remembered that monstrous eye in its buried vault -- but no, that was inconceivable. It was not organic life that he was watching: it was not even, be suspected, matter as he knew it.

The sombre red was brightening to an angrier hue. Streaks of vivid yellow appeared, so that for a moment Jan felt he was looking at a volcano pouring streams of lava down on to the land beneath. But these streams, as he could tell by occasional flecks and mottlings, were moving upwards.

Now something else was rising out of the ruby clouds around the mountain's base. It was a huge ring, perfectly horizontal and perfectly circular -- and it was the colour of all that Jan had left so far behind, for the skies of Earth had held no lovelier blue. Nowhere else on the world of the Overlords had he seen such hues, and his throat contracted with the longing and the loneliness they evoked.

The ring was expanding as it climbed. It was higher than the mountain now, and its nearer arc was sweeping swiftly towards him. Surely, thought Jan, it must be a vortex of some kind -- a smoke-ring already many kilometres across. But it showed none of the rotation he expected, and it seemed to grow no less solid as its size increased. Its shadow rushed past long before the ring itself had swept majestically overhead, still rising into space. He watched until it had dwindled to a thin thread of blue, hard for the eye to focus upon in the surrounding redness of the sky. When it vanished at last, it must already have been many thousands of kilometres across. And it was still growing.

He looked back at the mountain. It was golden now, and devoid of all markings. Perhaps it was imagination -- he could believe anything by this time -- but it seemed taller and narrower, and appeared to be spinning like the funnel of a cyclone. Not until then, still numbed and with his powers of reason almost in abeyance, did he remember his camera. He raised it to eye-level, and sighted towards that impossible, mind-shaking enigma.

Vindarten moved swiftly into his line of vision. With implacable firmness, the great hands covered the lens turret and forced him to lower the camera. Jan did not attempt to resist: it would have been useless, of course, but he felt a sudden deathly fear of that thing out there at the edge of the world, and wanted no further part of it.

There was nothing else in all his travels that they would not let him photograph, and Vindarten gave no explanations. Instead, he spent much time getting Jan to describe in minute detail what he had witnessed. It was then that Jan realized that Vindarten's eyes had seen something totally different: and it was then that he guessed, for the first time, that the Overlords had masters, too.

Now he was coming home, and all the wonder, the fear and the mystery were far behind. It was the same ship, he believed, though surely not the same crew. However long their lives, It was hard to believe that the Overlords would willingly cut themselves off from their home for all the decades consumed on an interstellar voyage.

It was of no importance now, for Earth was there ahead. He had seen it thus a hundred times before, but always through the remote, mechanical eye of the television camera. Now at last he himself was out here in space, as the final act of his dream unfolded itself; and Earth spun beneath on its eternal orbit. The great blue-green crescent was in its first quarter: more than half the visible disc was still in darkness. There was little cloud -- a few bands scattered along the line of the trade winds. The arctic cap glittered brilliantly, but was far outshone by the dazzling reflection of the sun in the north Pacific.

Had he wished, Jan could doubtless have stayed here for the remainder of his life. But Vindarten had warned him that there would be no other ship going to Earth for several years, and had advised him to take this opportunity. Perhaps the Overlords realized that even in this relatively short time, his mind had nearly reached the end of its resources. Or he might merely have become a nuisance, and they could spare no more time for him.

The Relativity time-dilation effect worked both ways, of course. The Overlords would age only four months on the round trip, but when they returned their friends would be eighty years older.

The ship was driving into Earth's great cone of shadow: the gleaming crescent dwindled, shrank to a burning bow of fire, and winked out of existence. Below was darkness and night. The world was sleeping.

One might have thought it was a world of water: this hemisphere was almost devoid of land. The only continent visible was Australia, a darker mist in the atmospheric haze along the limb of the planet.

It was then that Jan realized what was wrong. There was land down there -- but where were the gleaming necklaces of light, where were the glittering coruscations that had been the cities of man? In all that shadowy hemisphere, there was no single spark to drive back the night. Gone without a trace were the millions of kilowatts that once had been splashed carelessly towards the stars. He might have been looking down on Earth as it had been before the coming of man.

This was not the homecoming he had expected. There was nothing he could do but watch, while the fear of the unknown grew within him. Something had happened -- something unimaginable. And yet the ship was descending purposefully in a long curve that was taking it again over the sunlit hemisphere.

He saw nothing of the actual landing, for the picture of Earth suddenly winked out and was replaced by that meaning- less pattern of lines and lights. When vision was restored, they were on the ground. There were great buildings in the distance, machines moving about, and a group of Overlords watching them.

Karellen was standing, a little apart from his companions, beside a great transport vehicle loaded with crates. Jan did not stop to wonder how he recognized the Supervisor, nor was he surprised to see him completely unchanged. That was almost the only thing that had turned out as he had expected.

He was home, seeing once more by the sparkling light of his own familiar sun, breathing the air that had first washed through his lungs. The gangway was already down, but he had to wait for a moment until the glare outside no longer blinded him.

Somewhere there was the muffled roar of air as the ship equalized pressure, then the sound of great doors opening. He did not wait: the silent giants watched him with tolerance or indifference as he ran from the control room.

"I have been waiting for you," said Karellen.