'Are you sure he won't try anything?'

'Two-hundred-per-cent sure. Remember your precautions with Hal? I've already taken steps with Nina. Nobody flies her without my permission.'

'I still can't believe it. Are you sure Max wasn't pulling your leg?'

'His sense of humour isn't that subtle. Besides, be was pretty miserable at the time.'

'Oh – now I understand. It must have been when he had that row with Zenia. I suppose he wanted to impress her. Anyway, they seem to have got over it.'

'I'm afraid so,' Curnow answered wryly. Floyd could not help smiling; Curnow noticed it, and started to chuckle, which made Floyd laugh, which...

It was a splendid example of positive feedback in a high-gain loop. Within seconds, they were both laughing uncontrollably.

The crisis was over. What was more, they had taken the first step toward genuine friendship.

They had exchanged vulnerabilities.

40 – 'Daisy, Daisy...'

The sphere of consciousness in which he was embedded enclosed the whole of Jupiter's diamond core. He was dimly aware, at the limits of his new comprehension, that every aspect of the environment around him was being probed and analysed. Immense quantities of data were being gathered, not merely for storage and contemplation, but for action. Complex plans were being considered and evaluated; decisions were being made that might affect the destiny of worlds. He was not yet part of the process; but he would be.

NOW YOU ARE BEGINNING TO UNDERSTAND.

It was the first direct message. Though it was remote and distant, like a voice through a cloud, it was unmistakably intended for him. Before he could ask any of the myriad questions that raced through his mind, there was a sense of withdrawal, and once more he was alone.

But only for a moment. Closer and clearer came another thought, and for the first time he realized that more than one entity was controlling and manipulating him. He was involved in a hierarchy of intelligences, some close enough to his own primitive level to act as interpreters. Or perhaps they were all aspects of a single being.

Or perhaps the distinction was totally meaningless.

Of one thing, however, he was now sure. He was being used as a tool, and a good tool had to be sharpened, modified – adapted. And the very best tools were those that understood what they were doing.

He was learning that now. It was a vast and awesome concept, and he was privileged to be a part of it – even though he was aware of only the merest outlines. He had no choice but to obey, yet that did not mean that he must acquiesce to every detail, at least without a protest.

He had not yet lost all his human feeling; that would have made him valueless. The soul of David Bowman had passed beyond love, but it could still know compassion for those who had once been his colleagues.

VERY WELL came the answer to his plea. He could not tell whether the thought conveyed an amused condescension, or total indifference. But there was no doubt of its majestic authority as it continued: THEY MUST NEVER KNOW THAT THEY ARE BEING MANIPULATED. THAT WOULD RUIN THE PURPOSE OF THE EXPERIMENT.

Then there was a silence that he did not wish to breach again. He was still awed and shaken – as if, for a moment, he had heard the clear voice of God.

Now he was moving purely under his own volition, toward a destination he had chosen himself. The crystal heart of Jupiter fell below; the layers upon layers of helium and hydrogen and carbonaceous compounds flickered past. He had a glimpse of a great battle between something like a jellyfish, fifty kilometres across, and a swarm of spinning disks that moved more swiftly than anything he had yet seen in the Jovian skies. The jellyfish appeared to be defending itself with chemical weapons; from time to time it would emit jets of coloured gas and the disks touched by the vapour would start to wobble drunkenly, then slip downward like falling leaves until they had disappeared from sight. He did not stop to watch the outcome; he knew that it did not matter who were the victors and who the vanquished.

As a salmon leaps a waterfall, he flashed in seconds from Jupiter to Io, against the descending electric currents of the flux-tube. It was quiescent that day; only the power of a few terrestrial thunderstorms was flowing between planet and satellite. The gateway through which he had returned still floated in that current, shouldering it aside as it had done since the dawn of man.

And there, utterly dwarfed by the monument of a greater technology, was the vessel that had brought him from the little world of his birth.

How simple – how crude! – it now appeared. With a single scan, he could see innumerable flaws and absurdities in its design, as well as that of the slightly less primitive ship to which it was now coupled by a flexible, airtight tube.

It was hard to focus upon the handful of entities inhabiting the two ships; he could barely interact with the soft creatures of flesh and blood who drifted like ghosts through the metal corridors and cabins. For their part, they were totally unaware of his presence, and he knew better than to reveal himself too abruptly.

But there was someone with whom he could communicate in a mutual language of electric field and currents, millions of times more swiftly than with sluggish organic brains.

Even if he had been capable of resentment, he would have felt none toward Hal; he understood, then, that the computer had only chosen what seemed to be the most logical course of behaviour.

It was time to resume a conversation that had been interrupted, it seemed, only moments ago.

'Open the Pod Bay door, Hal.'

'I'm sorry, Dave – I can't do that.'

'What's the problem, Hal?'

'I think you know that as well as I do, Dave. This mission is much too important for you to jeopardize it.'

'I don't know what you are talking about. Open the Pod Bay door.'

'This conversation can serve no further useful purpose. Goodbye, Dave.'

He saw Frank Poole's body go drifting off toward Jupiter, as he abandoned his pointless mission of retrieval. Still remembering his anger at himself for having forgotten his helmet, he watched the emergency hatch open, felt the tingling of vacuum on the skin he no longer possessed, heard his ears pop – then knew, as few men had ever known, 'the utter silence of space. For an eternal fifteen seconds he fought to close the hatch and start the repressurization sequence, while trying to ignore the warning symptoms pouring into his brain. Once, in the school lab, he had spilled some ether on his hand and felt the touch of icy cold as the liquid swiftly evaporated. Now his eyes and lips remembered that sensation as their moisture boiled off into vacuum; his vision was blurred and he had to keep blinking lest his eyeballs freeze solid.

Then – what blessed relief! – he heard the roar of air, felt the restoration of pressure, was able to breathe again in great, hungry gasps.

'Just what do you think you are doing, Dave?'

He had not answered, as he drove with grim determination along the tunnel leading to the sealed vault that housed the brain of the computer. Hal had spoken truly: 'This conversation can no longer serve any useful purpose...'

'Dave – I really think I'm entitled to an answer to that question.'

'Dave – I can see you're really upset about this. I honestly think you ought to sit down calmly, take a stress pill, and think things over.'

'I know I've made some very poor decisions recently, but I can give my complete assurance that my work will be back to normal, I've still got the greatest confidence in the mission... and I want to help you.'

Now he was in the little red-lit chamber, with its neatly ranged rows and columns of solid-state units, looking rather like a bank's safe-deposit vault. He released the locking bar on the section labelled COGNITIVE FEEDBACK and pulled out the first memory block. The marvellously complex three-dimensional network, which could lie comfortably in a man's hand yet contained millions of elements, floated away across the vault.