There he had witnessed the paradox of sunrise on the face of a sun, when the dying star's brilliant white dwarf companion had climbed into its sky – a searing apparition, drawing a tidal wave of fire beneath it. He had felt no fear, but only wonder, even when his space pod had carried him down into the inferno below... to arrive, beyond all reason, in a beautifully appointed hotel suite containing nothing that was not wholly familiar. However, much of it was fake; the books on the shelves were dummies, the cereal boxes and the cans of beer in the icebox – though they bore famous labels – all contained the same bland food with a texture like bread but a taste that was almost anything he cared to imagine.

He had quickly realized that he was a specimen in a cosmic zoo, his cage carefully recreated from the images in old television programmes. And he wondered when his keepers would appear, and in what physical form.

How foolish that expectation had been! He knew now that one might as well hope to see the wind, or speculate about the true shape of fire.

Then exhaustion of mind and body had overwhelmed him. For the last time, David Bowman slept.

It was a strange sleep, for he was not wholly unconscious. Like a fog creeping through a forest, something invaded his mind. He sensed it only dimly, for the full impact would have destroyed him as swiftly and surely as the fires raging around him. Beneath its dispassionate scrutiny, he felt neither hope nor fear.

Sometimes, in that long sleep, he dreamed he was awake. Years had gone by; once he was looking in a mirror, at a wrinkled face he barely recognized as his own. His body was racing to its dissolution, the hands of the biological clock spinning madly toward a midnight they would never reach. For at the last moment, Time came to a halt – and reversed itself.

The springs of memory were being trapped: in controlled recollection, he was reliving his past, being drained of knowledge and experience as he swept back toward his childhood. But nothing was being lost: all that he had ever been, at every moment of his life, was being transferred to safer keeping. Even as one David Bowman ceased to exist, another became immortal, passing beyond the necessities of matter.

He was an embryo god, not yet ready to be born. For ages he floated in limbo, knowing what he had been, but not what he had become. He was still in a state of flux -somewhere between chrysalis and butterfly. Or perhaps only between caterpillar and chrysalis.

And then, the stasis was broken: Time re-entered his little world. The black, rectangular slab that suddenly appeared before him was like an old friend.

He had seen it on the Moon; he had encountered it in orbit around Jupiter; and he knew, somehow, that his ancestors had met it long ago. Though it held still unfathomed secrets, it was no longer a total mystery; some of its powers he now understood.

He realized that it was not one, but multitudes; and that whatever measuring instruments might say, it was always the same size – as large as necessary.

How obvious, now, was that mathematical ratio of its sides, the quadratic sequence 1:4:9! And how naive to have imagined that the series ended there, in only three dimensions!

Even as his mind focused upon these geometrical simplicities, the empty rectangle filled with stars. The hotel suite – if indeed it had ever really existed – dissolved back into the mind of its creator; and there before him was the luminous whirlpool of the Galaxy.

It might have been some beautiful, incredibly detailed model, embedded in a block of plastic. But it was the reality, now grasped by him as a whole with senses more subtle than vision. If he wished, he could focus his attention upon any one of its hundred billion stars.

Here he was, adrift in this great river of suns, halfway between the banked fires of the galactic core and the lonely, scattered sentinel stars of the rim. And there was his origin, on the far side of this chasm in the sky, this serpentine band of darkness, empty of all stars. He knew that this formless chaos, visible only by the glow that limned its edges from fire mists far beyond, was the still unused stuff of creation, the raw material of evolutions yet to be. Here, Time had not yet begun; not until the suns that now burned were long since dead would light and life reshape this void.

Unwittingly, he had crossed it once: now, far better prepared, though still wholly ignorant of the impulse that drove him, he must cross it again.

The Galaxy burst forth from the mental frame in which he had enclosed it: stars and nebulae poured past him in an illusion of infinite speed. Phantom suns exploded and fell behind as he slipped like a shadow through their cores.

The stars were thinning out, the glare of the Milky Way dimming into a pale ghost of the glory he had known – and might one day know again. He was back in the space that men called real, at the very point he had left it, seconds or centuries ago.

He was vividly aware of his surroundings, and far more conscious than in that earlier existence of myriad sensory inputs from the external world. He could focus upon any one of them, and scrutinize it in virtually limitless detail, until he confronted the fundamental, granular structure of time and space, below which there was only chaos.

And he could move, though he did not know how. But had he ever really known that, even when he possessed a body? The chain of command from brain to limb was a mystery to which he had never given any thought.

An effort of will, and the spectrum of that nearby star shifted toward the blue, by precisely the amount he wished. He was falling toward it at a large fraction of the speed of light: though he could go faster if he desired, he was in no hurry. There was still much information to be processed, much to be considered... and much more to be won. That, he knew, was his present goal; but he also knew that it was only part of some far wider plan, to be revealed in due course.

He gave no thought to the gateway between universes dwindling so swiftly behind him, or to the anxious entities gathered around it in their primitive spacecraft. They were part of his memories; but stronger ones were calling him now, calling him home to the world he had never thought to see again.

He could hear its myriad voices, growing louder and louder – as it too was growing, from a star almost lost against the Sun's outstretched corona, to a slim crescent, and finally to a glorious blue-white disk.

They knew that he was coming. Down there on that crowded globe, the alarms would be flashing across the radar screens, the great tracking telescopes would be searching the skies – and history as men had known it would be drawing to a close.

He became aware that a thousand kilometres below a slumbering cargo of death had awakened, and was stirring in its orbit. The feeble energies it contained were no possible menace to him; indeed, he could profitably use them.

He entered the maze of circuitry, and swiftly traced the way to its lethal core. Most of the branchings could be ignored; they were blind alleys, devised for protection. Beneath his scrutiny, their purpose was childishly simple; it was easy to bypass them all.

Now there was a single last barrier – a crude but effective mechanical relay, holding apart two contacts. Until they were closed, there would be no power to activate the final sequence.

He put forth his will – and, for the first time, knew failure and frustration. The few grams of the microswitch would not budge. He was still a creature of pure energy; as yet, the world of inert matter was beyond his grasp. Well, there was a simple answer to that.

He still had much to learn. The current pulse he induced in the relay was so powerful that it almost melted the coil, before it could operate the trigger mechanism.