Then who is speaking to me?

I WAS DAVID BOWMAN.

Floyd stared at the screen for a long time before making his next move. The joke, which had never been funny in the first place, had now gone too far. It was in the worst possible taste. Well, this should fix whoever was at the other end of the line.

I cannot accept that identification without some proof.

I UNDERSTAND. IT IS IMPORTANT THAT YOU BELIEVE ME. LOOK BEHIND YOU.

Even before that last chilling sentence appeared on the screen, Floyd had begun to doubt his hypothesis. The whole exchange had become very odd, though there was nothing definite on which he could put his finger. As a joke, it had become totally pointless.

And now – he felt a prickling in the small of his back. Very slowly – indeed, reluctantly – he swung his swivel chair around, away from the banked panels and switches of the computer display, toward the Velcro-covered catwalk behind.

The zero-gravity environment of Discovery's observation deck was always dusty, for the air-filtration plant had never been brought back to full efficiency. The parallel rays of the heatless yet still brilliant sun, streaming through the great windows, always lit up myriads of dancing motes, drifting in stray currents and never settling anywhere – a permanent display of Brownian movement.

Now something strange was happening to those particles of dust; some force seemed to be marshalling them, herding them away from a central point yet bringing others toward it, until they all met on the surface of a hollow sphere. That sphere, about a metre across, hovered in the air for a moment like a giant soap bubble – but a granular one, lacking a bubble's characteristic iridescence. Then it elongated into an ellipsoid, its surface began to pucker, to form folds and indentations.

Without surprise – and almost without fear – Floyd realized that it was assuming the shape of a man.

He had seen such figures, blown out of glass, in museums and science exhibitions. But this dusty phantom did not even approximate anatomical accuracy; it was like a crude clay figurine, or one of the primitive works of art found in the recesses of a Stone Age cave. Only the head was fashioned with any care; and the face, undoubtedly, was that of Commander David Bowman.

There was a faint murmur of white noise from the computer panel behind Floyd's back. Hal was switching from visual to audio output.

'Hello, Dr Floyd. Now do you believe me?'

The lips of the figure never moved; the face remained a mask. But Floyd recognized the voice, and all remaining doubts were swept away.

'This is very difficult for me, and I have little time. I have been... allowed to give this warning. You have only fifteen days.'

'But why – and what are you? Where have you been?'

There were a million questions he wanted to ask – yet the ghostly figure was already fading, its grainy envelope beginning to dissolve back into the constituent particles of dust. Floyd tried to freeze the image in his mind, so that later he could convince himself that it was really happening – and not a dream as that first encounter with TMA-1 now sometimes seemed to be.

How strange, that he, out of all the billions of humans who had ever lived on planet Earth, had been privileged to make contact not once but twice with another form of intelligence! For he knew that the entity addressing him must be something far more than David Bowman.

It was also something less. Only the eyes – who had once called them the 'windows of the soul'? – had been accurately reproduced. The rest of the body was a featureless blank, lacking all detail. There was no hint of genitals or sexual characteristics; that in itself was a chilling indication of how far David Bowman had left his human heritage behind.

'Goodbye, Dr Floyd. Remember – fifteen days. We can have no further contact. But there may be one more message, if all goes well.'

Even as the image dissolved, taking with it his hopes of opening up a channel to the stars, Floyd could not help smiling at that old Space Age cliché. 'If all goes well' – how many times had he heard that phrase before some mission! And did it mean that they – whoever they might be – were also sometimes uncertain of the outcome? If so, that was strangely reassuring. They were not omnipotent. Others might still hope and dream – and act.

The phantom was gone; only the motes of dancing dust were left, resuming their random patterns in the air.

VI – DEVOURER OF WORLDS

42 – The Ghost in the Machine

'I'm sorry, Heywood – I don't believe in ghosts. There must be a rational explanation. There's nothing that the human mind can't account for.'

'I agree, Tanya. But let me remind you of Haldane's famous remark: The Universe is not only stranger than we imagine – but stranger than we can imagine.'

'And Haldane,' Curnow interjected mischievously, 'was a good Communist.'

'Perhaps so, but that particular saying can be used to support all kinds of mystical nonsense. Hal's behaviour must be the result of some kind of programming. The personality he created has to be an artifact of some kind. Don't you agree, Chandra?'

That was waving a red flag in front of a bull; Tanya had to be desperate. However, Chandra's reaction was surprisingly mild, even for him. He seemed to be preoccupied, as if he was indeed seriously considering the possibility of another computer malfunction.

'There must have been some external input, Captain Orlova. Hal could not have created such a self-consistent audiovisual illusion out of nothing. If Dr Floyd is reporting accurately, someone was in control. And in real time, of course, since there was no delay in the conversation.'

'That makes me number-one suspect,' exclaimed Max. 'I was the only other person awake.'

'Don't be ridiculous, Max,' retorted Nikolai. 'The audio side would have been easy, but there's no way that apparition could have been arranged, without some very elaborate equipment. Laser beams, electrostatic fields – I don't know. Maybe a stage magician could do it, but he'd need a truck-load of props.'

'Just a moment!' said Zenia brightly. 'If this really happened, surely Hal will remember and you could ask...'

Her voice died away as she saw the glum expressions around her. Floyd was the first to take pity on her embarrassment.

'We tried that, Zenia; he has absolutely no recollection of the phenomenon. But as I've already pointed out to the others, that doesn't prove anything. Chandra's shown how Hal's memories can be selectively erased – and the auxiliary speech-synthesizer modules have nothing to do with the mainframe. They could be operated without Hal knowing anything about it...' He paused for breath, then launched his pre-emptive strike.

'I admit that this doesn't leave many alternatives. Either I was imagining the whole thing, or it really happened. I know it wasn't a dream, but I can't be sure it wasn't some kind of hallucination. But Katerina's seen my medical reports – she knows I wouldn't be here if I had that sort of problem. Still, it can't be ruled out – and I won't blame anyone for making it their number-one hypothesis. I'd probably do the same.

'The only way I can prove it wasn't a dream is to get some supporting evidence. So let me remind you of the other strange things that have happened recently. We know that Dave Bowman went into Big Bro – Zagadka. Something came out, and headed for Earth. Vasili saw it – I didn't! Then there was the mysterious explosion of your orbiting bomb,

'Yours.'

'Sorry – the Vatican's, And it does seem rather curious that soon afterward old Mrs Bowman died very peacefully, for no apparent medical reason. I'm not saying there's any connection, but – well, do you know the saying: Once is an accident; twice is a coincidence; three times is a conspiracy.'