"All political problems," Karellen had once told Stormgren, "can be solved by the correct application of power."

"The operative word is correct. You have never possessed real power, or the knowledge necessary to apply it. As in all problems, there are efficient and inefficient approaches. Suppose, for example, that one of your nations, led by some fanatical ruler, tried to revolt against me. The highly inefficient answer to such a threat would be some billions of horsepower in the shape of atomic bombs. If I used enough bombs, the solution would be complete and final. It would also, as I remarked, be inefficient -- even if it possessed no other defects."

Fifty years is ample time in which to change a world and its people almost beyond recognition. All that is required for the task are a sound knowledge of social engineering, a clear sight of the intended goal -- and power. These things the Overlords possessed. Though their goal was hidden, their knowledge was obvious -- and so was their power.

"That sounds a rather cynical remark," Stormgren had replied doubtfully. "It's a little too much like 'Might is Right'. In our own past, the use of power has been notably unsuccessful in solving anything."

That power took many forms, few of them realized by the peoples whose destinies the Overlords now ruled. The might enshrined in their great ships had been clear enough for every eye to see. But behind that display of sleeping force were other and much subtler weapons.

"That requires about as much power as a small radio transmitter -- and rather similar skills to operate. For it's the application of the power, not its amount, that matters. How long do you think Hitler's career as dictator of Germany would have lasted, if wherever he went a voice was talking quietly in his ear? Or if' a steady musical note, loud enough to drown all other sounds and to prevent sleep, filled his brain night and day? Nothing brutal, you appreciate. Yet, in the final analysis, just as irresistible as a tritium bomb."

"I see," said Stormgren; "and there would be no place to hide?"

Yet, by their mere presence, they had changed the history of Earth. Now their task was done, and their achievement lingered behind them to go echoing down the centuries.

"And the efficient solution?"

"No place where I could not send my -- ah -- devices if I felt sufficiently strongly about it. And that is why I shall never have to use really drastic methods to maintain my position."

The great ships, then, had never been more than symbols, and now the world knew that all save one had been phantoms.

Karellen's calculations had been accurate. The shock of revulsion had passed swiftly, though there were many who prided themselves on their freedom from superstition yet would never be able to face one of the Overlords. There was something strange here, something beyond all reason or logic.

In the Middle Ages, people believed in the devil and feared him. But this was the twenty-first century; could it be that, after all, there was such a thing as racial memory?

It was, of course, universally assumed that the Overlords, or beings of the same species, had come into violent conflict with ancient man. The meeting must have lain in the remote past, for it had left no traces in recorded history. Here was another puzzle, and Karellen would give no help in its solution.

The Overlords, though they had now shown themselves to man, seldom left their one remaining ship. Perhaps they found it physically uncomfortable on Earth, for their size, and the existence of their wings, indicated that they came from a world of much lower gravity. They were never seen without a belt adorned with complex mechanisms which, it was generally believed, controlled their weight and enabled them to communicate with each other. Direct sunlight was painful to them, and they never stayed in it for more than a few seconds. When they had to go into the open for any length of time, they wore dark glasses which gave them a somewhat incongruous appearance. Though they seemed able to breathe terrestrial air, they sometimes carried small cylinders of gas from which they refreshed themselves occasionally.

In many ways, the appearance of the Overlords had raised more problems than it had solved. Their origin was still unknown, their biology a source of endless speculation. On many matters they would give information freely, but on others their behaviour could only be described as secretive. On the whole, however, this did not annoy anyone except the scientists. The average man, though he might prefer not to meet the Overlords, was grateful to them for what they had done to his world.

Perhaps these purely physical problems accounted for their aloofness. Only a small fraction of the human race had ever actually met an Overlord in the flesh, and no one could guess how many of them were aboard Karellen's ship. No more than five had ever been seen together at one time, but there might be hundreds, even thousands of them aboard that tremendous vessel.

By the standards of all earlier ages, it was Utopia. Ignorance, disease, poverty and fear had virtually ceased to exist. The memory of war was fading into the past as a nightmare vanishes with the dawn; soon it would lie outside the experience of all living men.

It was One World. The old names of the old countries were still used, but they were no more than convenient postal divisions. There was no one on earth who could not speak English, who could not read, who was not within range of a television set, who could not visit the other side of the planet within twenty-four hours.

With the energies of mankind directed into constructive channels, the face of the world had been remade. It was, almost literally, a new world. The cities that had been good enough for earlier generations had been rebuilt -- or deserted and left as museum specimens when they had ceased to serve any useful purpose. Many cities had already been abandoned in this manner, for the whole pattern of industry and commerce had changed completely. Production had become largely automatic: the robot factories poured forth consumer goods in such unending streams that all the ordinary necessities of life were virtually free. Men worked for the sake of the luxuries they desired; or they did not work at all.

Crime had practically vanished. It had become both not necessary and impossible. When no one lacks anything, there is no point in stealing. Moreover, all potential criminals knew that there could be no escape from the surveillance of the Overlords. In the early days of their rule, they had intervened so effectively on behalf of law and order that the lesson had never been forgotten.

Crimes of passion, though not quite extinct, were almost unheard of. Now that so many of its psychological problems had been removed, humanity was far saner and less irrational. And what earlier ages would have called vice was now no more than eccentricity -- or, at the worst, bad manners.

One of the most noticeable changes had been a slowing-down of the mad tempo that had so characterized the twentieth century. Life was more leisurely than it had been for generations. It therefore had less zest for the few, but more tranquillity for the many. Western man had relearned -- what the rest of the world had never forgotten -- that there was nothing sinful in leisure as long as it did not degenerate into mere sloth.

Whatever problems the future might bring, time did not yet hang heavy on humanity's hands. Education was now much more thorough and much more protracted. Few people left college before twenty -- and that was merely the first stage, since they normally returned again at twenty-five for at least three more years, after travel and experience had broadened their minds. Even then, they would probably take refresher courses at intervals for the remainder of their lives in the subjects that particularly interested them.

This extension of human apprenticeship so far past the beginning of physical maturity had given rise to many social changes. Some of these had been necessary for generations, but earlier periods had refused to face the challenge -- or had pretended that it did not exist. In particular, the pattern of sexual mores -- insofar as there had ever been a single pattern -- had altered radically. It had been virtually shattered by two inventions, which were, ironically enough, of purely human origin and owed nothing to the Overlords. The first was a completely reliable oral contraceptive; the second was an equally infallible method -- as certain as fingerprinting, and based on a very detailed analysis of the blood -- of identifying the father of any child. The effect of these two inventions upon human society could only be described as devastating, and they had swept away the last remnants of the Puritan aberration.

Another great change was the extreme mobility of the new society. Thanks to the perfection of air-transport, everyone was free to go anywhere at a moment's notice. There was more room in the skies than there had ever been on the roads, and the, twenty-first century had repeated, on a larger scale, the great American achievement of putting a nation on wheels. It had given wings to the world.

Though not literally. The ordinary private flyer or air-car had no wings at all, or indeed any visible control surfaces. Even the clumsy rotor blades of the old helicopters had been banished. Yet Man had not discovered anti-gravity; only the Overlords possessed that ultimate secret. His air-cars were propelled by forces which the Wright brothers would have understood. Jet reaction, used both directly and in the more subtle form of boundary layer control, drove his flyers forward and held them in the air. As no laws or edicts of the Overlords could have done, the ubiquitous little air-cars had washed away the last barriers between the different tribes of mankind.

Perhaps the old faiths would have lingered for generations yet, had it not been for human curiosity. It was known that the Overlords had access to the past, and more than once historians had appealed to Karellen to settle some ancient contro- versy. It may have been that he had grown tired of such questions, but it is more likely that he knew perfectly well what the outcome of his generosity would be…

Profounder things had also passed. It was a completely secular age. Of the faiths that had existed before the coming of the Overlords, only a form of purified Buddhism -- perhaps the most austere of all religions -- still survived. The creeds that had been based upon miracles and revelations had collapsed utterly. With the rise of education, they had already been slowly dissolving, but for a while the Overlords had taken no sides in the matter. Though Karellen was often asked to express his views on religion, all that he would say was that a man's beliefs were his own affair, so long as they did not interfere with the liberty of others.

Though it had always been obvious to any rational mind that all the world's religious writings could not be true, the shock was nevertheless profound. Here was a revelation which no one could doubt or deny: here, seen by some unknown magic of Overlord science, were the true beginnings of all the world's great faiths. Most of them were noble and inspiring -- but that was not enough. Within a few days, all mankind's multitudinous messiahs had lost their divinity. Beneath the fierce and passionless light of truth, faiths that had sustained millions for twice a thousand years vanished like morning dew. All the good and all the evil they had wrought were swept suddenly into the past, and could touch the minds of men no more.

The instrument he handed over on permanent loan to the World History Foundation was nothing more than a television receiver with an elaborate set of controls for determining coordinates in time and space. It must have been linked somehow to a far more complex machine, operating on principles that no one could imagine, aboard Karellen's ship. One had merely to adjust the controls, and a window into the past was opened up. Almost the whole of human history for the past five thousand years became accessible in an instant. Earlier than that the machine would not go, and there were baffling blanks all down the ages. They might have had some natural cause, or they might be due to deliberate censorship by the Overlords.

This decline had been partly disguised by an enormous efflorescence of the descriptive sciences such as zoology, botany and observational astronomy. There had never been so many amateur scientists gathering facts for their own amusement -- but there were few theoreticians correlating these facts.

The end of strife and conflicts of all kinds had also meant the virtual end of creative art. There were myriads of performers, amateur and professional, yet there had, been no really outstanding new works of literature, music, painting or sculpture for a generation. The world was still living on the glories of a past that could never return.

Though few realized it as yet, the fall of religion had been paralleled by a decline in science. There were plenty of technologists, but few original workers extending the frontiers of human knowledge. Curiosity remained, and the leisure to indulge in it, but the heart had been taken out of fundamental scientific research. It seemed futile to spend a lifetime searching for secrets that the Overlords had probably uncovered ages before.

Humanity had lost its ancient gods; now it was old enough to have no need for new ones.

No one worried except a few philosophers. The race was too intent upon savouring its new-found freedom to look beyond the pleasures of the present. Utopia was here at last; its novelty had not yet been assailed by the supreme enemy of all Utopias -- boredom.

If, indeed, it was altruism. For there were still some who wondered if the policies of the Overlords would always coincide with the true welfare of humanity.

Perhaps the Overlords had the answer to that, as they had to all other problems. No one knew -- any more than they knew, a lifetime after their arrival -- what their ultimate purpose might be. Mankind had grown to trust them, and to accept without question the superhuman altruism that had kept Karellen and his companions so long exiled from their homes.