'Then what do you suggest?' Tanya asked, in a voice that now held a distinct note of menace.

'We must tell him the whole truth, as far as we know it – no more lies or half-truths, which are just as bad. And then let him decide for himself.'

'Hell, Chandra – he's only a machine!'

Chandra looked at Max with such a steady, confident gaze that the younger man quickly dropped his eyes.

'So are we all, Mr Brailovsky. It is merely a matter of degree. Whether we are based on carbon or on silicon makes no fundamental difference; we should each be treated with appropriate respect.'

It was strange, thought Floyd, how Chandra – much the smallest person in the room – now seemed the largest. But the confrontation had gone on far too long. At any moment Tanya would start to issue direct orders, and the situation would become really nasty.

'Tanya, Vasili – can I have a word with you both? I think there is a way of resolving the problem.'

Floyd's interruption was received with obvious relief, and two minutes later he was relaxing with the Orlovs in their quarters. (Or 'sixteenths', as Curnow had once christened them because of their size. He had soon regretted the pun, because he had to explain it to everyone except Sasha.)

'Thank you, Woody,' said Tanya, as she handed him a bulb of his favourite Azerbaijan Shemakha. 'I was hoping you'd do that. I suppose you have something – how do you put it? – up your sleeve.'

'I believe so,' Floyd answered, squirting a few cubic centimetres of the sweet wine into his mouth and savouring it gratefully. 'I'm sorry if Chandra is being difficult.'

'So am I. What a good thing we have only one mad scientist aboard.'

'That's not what you've sometimes told me,' grinned Academician Vasili. 'Anyway, Woody – let's have it.'

'This is what I suggest. Let Chandra go ahead and do it his way. Then there are just two possibilities.

'First, Hal will do exactly what we ask – control Discovery during the two firing periods. Remember, the first isn't critical. If something goes wrong while we're pulling away from Io, there's plenty of time to make corrections. And that will give us a good test of Hal's... willingness to cooperate.'

'But what about the Jupiter flyby? That's the one that really counts. Not only do we burn most of Discovery's fuel there, but the timing and thrust vectors have to be exactly right.'

'Could they be controlled manually?'

'I'd hate to try. The slightest error, and we'd either burn up, or become a long-period comet. Due again in a couple of thousand years.'

'But if there was no alternative?' Floyd insisted.

'Well, assuming we could take control in time, and had a good set of alternative orbits precomputed – um, perhaps we might get away with it.'

'Knowing you, Vasili, I'm sure that "might" means "would". Which leads me to the second possibility I mentioned. If Hal shows the slightest deviation from the program – we take over.'

'You mean – disconnect him?'

'Exactly.'

'That wasn't so easy last time.'

'We've learned a few lessons since then. Leave it to me. I can guarantee to give you back manual control in about half a second.'

'There's no danger, I suppose, that Hal will suspect anything?'

'Now you're getting paranoiac, Vasili. Hal's not that human. But Chandra is – to give him the benefit of the doubt. So don't say a word to him. We all agree with his plan completely, are sorry that we ever raised any objections, and are perfectly confident that Hal will see our point of view. Right, Tanya?'

'Right, Woody. And I congratulate you on your foresight; that little gadget was a good idea.'

'What gadget?' asked Vasili.

'I'll explain one of these days. Sorry, Woody – that's all the Shemakha you can have. I want to save it – until we're safely on the way to Earth.'

46 – Countdown

No one would ever believe this without my photos, thought Max Brailovsky as he orbited the two ships from half a kilometre away. It seems comically indecent, as if Leonov is raping Discovery. And now that he came to think of it, the rugged, compact Russian ship did look positively male, when compared with the delicate, slender American one. But most docking operations had distinctly sexual overtones, and he remembered that one of the early cosmonauts – he couldn't recall the name – had been reprimanded for his too vivid choice of words at the – er, climax of his mission.

As far as he could tell from his careful survey, everything was in order. The task of positioning the two ships and securing them firmly together had taken longer than anticipated. It would never have been possible at all without one of those strokes of luck that sometimes – not always -favour those who deserve them. Leonov had providentially carried several kilometres of carbon filament tape, no bigger than the ribbon a girl might use to tie her hair, yet capable of taking a strain of many tons. It had been thoughtfully provided to secure instrument packages to Big Brother if all else failed. Now it wrapped Leonov and Discovery in tender embrace – sufficiently firmly, it was hoped, to prevent any rattlings and shakings at all accelerations up to the one-tenth of a gravity that was the maximum that full thrust could provide.

'Anything more you want me to check before I come home?' asked Max.

'No,' replied Tanya. 'Everything looks fine. And we can't waste any more time.'

That was true enough. If that mysterious warning was to be taken seriously – and everyone now took it very seriously indeed – they should start their escape manoeuvre within the next twenty-four hours.

'Right – I'm bringing Nina back to the stable. Sorry about this, old girl.'

'You never told us Nina was a horse.'

'I'm not admitting it now. And I feel bad about dumping her here in space, just to give us a miserable few extra metres per second.'

'We may be very glad of them in a few hours, Max. Anyway, there's always a chance that someone may come and pick her up again, one day.'

I very much doubt it, thought Max. And perhaps, after all, it was appropriate to leave the little space pod there, as a permanent reminder of Man's first visit to the kingdom of Jupiter.

With gentle, carefully timed pulses from the control jets he brought Nina around the great sphere of Discovery's main life-support module; his colleagues on the flight deck barely glanced at him as he drifted past their curving window. The open Pod Bay door yawned before him, and he jockeyed Nina delicately down on to the extended docking arm.

'Pull me in,' he said, as soon as the latches had clicked shut. 'I call that a well-planned EVA. There's a whole kilogram of propellant left to take Nina out for the last time.'

Normally, there was little drama about a burn in deep space; it was not like the fire and thunder – and always present risks – of a lift-off from a planetary surface. If something went wrong, and the motors failed to come up to full thrust – well, matters could usually be corrected by a slightly longer burn. Or one could wait until the appropriate point in orbit, and try again.

But this time, as the countdown proceeded toward zero, the tension aboard both ships was almost palpable. Everyone knew that it was the first real test of Hal's docility; only Floyd, Curnow, and the Orlovs realized that there was a back-up system. And even they were not absolutely sure that it would work.

'Good luck, Leonov,' said Mission Control, timing the message to arrive five minutes before ignition. 'Hope everything's running smoothly. And if it's not too much trouble, could you please get some close-ups of the equator, longitude 115, as you go around Jupiter. There's a curious dark spot there – presumably some kind of upwelling, perfectly round, almost a thousand kilometres across. Looks like the shadow of a satellite, but it can't be.'