The ABORT program, peacefully sleeping ever since Galaxy was launched, took over and hurled the ship back up into the sky.

In the wardroom, the sudden surge of full thrust came like a stay of execution. The horrified officers had seen the collapse of the chosen landing site, and knew that there was only one way of escape. Now that Chang had taken it, they once more permitted themselves the luxury of breath.

But how long they could continue to enjoy that experience, no-one could guess. Only Chang knew whether the ship had enough propellant to reach a stable orbit; and even if it did, Captain Laplace thought gloomily, the lunatic with the gun might order him down again. Though he did not for a minute believe that she really was a lunatic; she knew exactly what she was doing.

Suddenly, there was a change in thrust.

'Number Four motor's just cut,' said an engineering officer. 'I'm not surprised – probably overheated. Not rated for so long at this level.'

There was, of course, no sense of any directional change – the reduced thrust was still along the ship's axis – but the views on the monitor screens had tilted crazily. Galaxy was still ascending, but no longer vertically. She had become a ballistic missile, aimed at some unknown target on Europa.

Once more, the thrust dropped abruptly; across the video monitors, the horizon became level again.

'He's cut the opposite motor – only way to stop us cartwheeling – but can he maintain altitude – good man!'

The watching scientists could not see what was good about it; the view on the monitors had disappeared completely, obscured by a blinding white fog.

'He's dumping excess propellant – lightening the ship -'

The thrust dwindled away to zero; the ship was in free fall. In a few seconds, it had dropped through the vast cloud of ice crystals created when its dumped propellant had exploded into space. And there beneath it, approaching at a leisurely one-eighth of a gravity acceleration, was Europa's central sea. At least Chang would not have to select a landing site; from now on, it would be standard operating procedure, familiar as a video game to millions who had never gone into space, and never would.

All you had to do was to balance the thrust against gravity, so that the descending ship reached zero velocity at zero altitude. There was some margin for error, but not much, even for the water landings which the first American astronauts had preferred, and which Chang was now reluctantly emulating. If he made a mistake – and after the last few hours, he could scarcely be blamed – no home computer would say to him: 'Sorry – you've crashed. Would you like to try again? Answer YES/NO...'

Second Officer Yu and his two companions, waiting with their improvised weapons outside the locked door of the bridge, had perhaps been given the toughest assignment of all. They had no monitor screens to tell them what was happening, and had to rely on messages from the wardroom. Nor had there been anything through the spy mike, which was hardly surprising. Chang and McCullen had very little time or need for conversation.

The touchdown was superb, with hardly a jolt. Galaxy sank a few extra metres, then bobbed up again, to float vertically and – thanks to the weight of the engines – in the upright position.

It was then that the listeners heard the first intelligible sounds through the spy mike.

'You maniac, Rosie,' said Chang's voice, more in resigned exhaustion than anger. 'I hope you're satisfied. You've killed us all.'

There was one pistol shot, then a long silence.

Yu and his colleagues waited patiently, knowing that something was bound to happen soon. Then they heard the locking levers being unlatched, and gripped the spanners and metal bars they were carrying. She might get one of them, but not all -The door swung open, very slowly.

'Sorry,' said Second Officer Chang. 'I must have passed out for a minute.'

Then, like any reasonable man, he fainted again.

I can never understand how a man could become a doctor, Captain Laplace told himself. Or an undertaker, for that matter. They have some nasty jobs to do...

'Well, did you find anything?'

'No, Skipper. Of course, I don't have the right sort of equipment. There are some implants that you could only locate through a microscope – or so I'm told. They could only be very short range, though.'

'Perhaps to a relay transmitter somewhere in the ship – Floyd's suggested we make a search. You took fingerprints and – any other idents?'

'Yes – when we contact Ganymede, we'll beam them up, with her papers. But I doubt if we'll ever know who Rosie was, or who she was acting for. Or why, for God's sake.'

'At least she showed some human instincts,' said Laplace thoughtfully. 'She must have known she'd failed, when Chang pulled the ABORT lever. She could have shot him then, instead of letting him land.'

'Much good that will do us, I'm afraid. Let me tell you something that happened when Jenkins and I put the cadaver out through the refuse dump.'

The doctor pursed his lips in a grimace of distaste.

'You were right, of course – it was the only thing to do. Well, we didn't bother to attach any weights – it floated for a few minutes – we watched to see if it would clear the ship – and then...'

The doctor seemed to be struggling for words.

'What, dammit?'

'Something came up out, of the water, Like a parrot beak, but about a hundred times bigger. It took – Rosie – with one snap, and disappeared. We have some impressive company here; even if we could breathe outside, I certainly wouldn't recommend swimming -'

'Bridge to Captain,' said the officer on duty, 'Big disturbance in the water – camera three – I'll give you the picture.'

'That's the thing I saw!' cried the doctor. He felt a sudden chill at the inevitable, ominous thought: I hope it's not back for more.

Suddenly, a vast bulk broke through the surface of the ocean and arched into the sky. For a moment, the whole monstrous shape was suspended between air and water.

The familiar can be as shocking as the strange – when it is in the wrong place. Both captain and doctor exclaimed simultaneously: 'It's a shark!'

There was just time to notice a few subtle differences – in addition to the monstrous parrot-beak – before the giant crashed back into the sea. There was an extra pair of fins – and there appeared to be no gills. Nor were there any eyes, but on either side of the beak there were curious protuberances that might be some other sense organs.

'Convergent evolution, of course,' said the doctor. 'Same problems, same solutions, on any planet. Look at Earth. Sharks, dolphins, ichthyosaurs – all oceanic predators must have the same basic design. That beak puzzles me, though -'

'What's it doing now?'

The creature had surfaced again, but now it was moving very slowly, as if exhausted after that one gigantic leap. In fact, it seemed to be in trouble – even in agony; it was beating its tail against the sea, without attempting to move in any definite direction.

Suddenly, it vomited its last meal, turned belly up, and lay wallowing lifelessly in the gentle swell.

'Oh my God,' whispered the Captain, his voice full of revulsion. 'I think I know what's happened.'

'Totally alien biochemistries,' said the doctor; even he seemed shaken by the sight. 'Rosie's claimed one victim, after all.'

The Sea of Galilee was, of course, named after the man who had discovered Europa – as he in turn had been named after a much smaller sea on another world.

It was a very young sea, being less than fifty years old; and, like most new-born infants, could be quite boisterous. Although the Europan atmosphere was still too thin to generate real hurricanes, a steady wind blew from the surrounding land towards the tropical zone at the point above which Lucifer was stationary. Here, at the point of perpetual noon, the water was continually boiling – though at a temperature, in this thin atmosphere, barely hot enough to make a good cup of tea.