'It wasn't necessary,' Floyd answered rather glumly. 'The State Department's already done it for me – with variations. We'll just have to see which one the Chinese come up with. And I wouldn't be in the least surprised if they outguess us again.'

Sleeping in zero gravity is a skill that has to be learned; it had taken Floyd almost a week to find the best way of anchoring legs and arms so that they did not drift into uncomfortable positions. Now he was an expert, and was not looking forward to the return of weight; indeed, the very idea gave him occasional nightmares.

Someone was shaking him awake. No – he must still be dreaming! Privacy was sacred aboard a spaceship; nobody ever entered another crew member's chambers without first asking permission. He clenched his eyes shut, but the shaking continued.

'Dr Floyd – please wake up! You're wanted on the flight deck!'

And nobody called him Dr Floyd; the most formal salutation he had received for weeks was Doc. What was happening?

Reluctantly, he opened his eyes. He was in his tiny cabin, gently gripped by his sleeping cocoon. So one part of his mind told him; then why was he looking at – Europa? They were still millions of kilometres away.

There were the familiar reticulations, the patterns of triangles and polygons formed by intersecting lines. And surely that was the Grand Canal itself – no, it wasn't quite right. How could it be, since he was still in his little cabin aboard Leonov?

'Dr Floyd!'

He became fully awake, and realized that his left hand was floating just a few centimetres in front of his eyes. How strange that the pattern of lines across the palm was so uncannily like the map of Europa! But economical Mother Nature was always repeating herself, on such vastly different scales as the swirl of milk stirred into coffee, the cloud lanes of a cyclonic storm, the arms of a spiral nebula.

'Sorry, Max,' he said. 'What's the problem? Is something wrong?'

'We think so – but not with us. Tsien's in trouble.'

Captain, navigator, and chief engineer were strapped in their seats on the flight deck; the rest of the crew orbited anxiously around convenient handholds, or watched on the monitors.

'Sorry to wake you up, Heywood,' Tanya apologized brusquely. 'Here's the situation. Ten minutes ago we had a Class One Priority from Mission Control. Tsien's gone off the air. It happened very suddenly, in the middle of a cipher message; there were a few seconds of garbled transmission – then nothing.'

'Their beacon?'

'That's stopped as well. We can't receive it either,'

'Phew! Then it must be serious – a major breakdown. Any theories?'

'Lots – but all guesswork. An explosion – landslide – earthquake: who knows?'

'And we may never know – until someone else lands on Europa – or we do a close flyby and take a look.'

Tanya shook her head. 'We don't have enough delta-vee. The closest we could get is fifty thousand kilometres. Not much you could see from that distance.'

'Then there's absolutely nothing we can do.'

'Not quite, Heywood. Mission Control has a suggestion. They'd like us to swing our big dish around, just in case we can pick up any weak emergency transmissions. It's – how do you say? – a long shot, but worth trying. What do you think?'

Floyd's first reaction was strongly negative.

'That will mean breaking our link with Earth.'

'Of course; but we'll have to do that anyway, when we go around Jupiter. And it will only take a couple of minutes to re-establish the circuit.'

Floyd remained silent. The suggestion was perfectly reasonable, yet it worried him obscurely. After puzzling for several seconds, he suddenly realized why he was so opposed to the idea.

Discovery's troubles had started when the big dish – the main antenna complex – had lost its lock on Earth, for reasons which even now were not completely clear. But Hal had certainly been involved, and there was no danger of a similar situation arising here. Leonov's computers were small, autonomous units; there was no single controlling intelligence. At least, no nonhuman one.

The Russians were still waiting patiently for his answer.

'I agree,' he said at last. 'Let Earth know what we're doing, and start listening. I suppose you'll try all the SPACE MAYDAY frequencies.'

'Yes, as soon as we've worked out the Doppler corrections. How's it going, Sasha?'

'Give me another two minutes, and I'll have the automatic search running. How long should we listen?'

The captain barely paused before giving her answer. Floyd had often admired Tanya Orlova's decisiveness, and had once told her so. In a rare flash of humour, she had replied: 'Woody, a commander can be wrong, but never uncertain.'

'Listen for fifty minutes, and report back to Earth for ten. Then repeat the cycle.'

There was nothing to see or hear; the automatic circuits were better at sifting the radio noise than any human senses. Nevertheless, from time to time Sasha turned up the audio monitor, and the roar of Jupiter's radiation belts filled the cabin. It was a sound like the waves breaking on all the beaches of Earth, with occasional explosive cracks from superbolts of lightning in the Jovian atmosphere. Of human signals, there was no trace; and, one by one, the members of the crew not on duty drifted quietly away.

While he was waiting, Floyd did some mental calculations. Whatever had happened to Tsien was already two hours in the past, since the news had been relayed from Earth.

But Leonov should be able to pick up a direct message after less than a minute's delay, so the Chinese had already had ample time to get back on the air. Their continued silence suggested some catastrophic failure, and he found himself weaving endless scenarios of disaster.

The fifty minutes seemed like hours. When they were up, Sasha swung the ship's antenna complex back toward Earth, and reported failure. While he was using the rest of the ten minutes to send a backlog of messages, he looked inquiringly at the captain.

'Is it worth trying again?' he said in a voice that clearly expressed his own pessimism.

'Of course. We may cut back the search time – but we'll keep listening.'

On the hour, the big dish was once more focused upon Europa. And almost at once, the automatic monitor started flashing its ALERT light.

Sasha's hand darted to the audio gain, and the voice of Jupiter filled the cabin. Superimposed upon that, like a whisper heard against a thunderstorm, was the faint but completely unmistakable sound of human speech. It was impossible to identify the language, though Floyd felt certain, from the intonation and rhythm, that it was not Chinese, but some European tongue.

Sasha played skilfully with fine-tuning and band-width controls, and the words became clearer. The language was undoubtedly English – but its content was still maddeningly unintelligible.

There is one combination of sounds that every human ear can detect instantly, even in the noisiest environment. When it suddenly emerged from the Jovian background, it seemed to Floyd that he could not possibly be awake, but was trapped in some fantastic dream. His colleagues took a little longer to react; then they stared at him with equal amazement – and a slowly dawning suspicion.

– For the first recognizable words from Europa were: 'Dr Floyd – Dr Floyd – I hope you can hear me.'