Anawak joined her. 'One of many possible worlds, right?'

Crowe nodded.

'Did any of your scenarios provide for an underwater alien civilisation?'

'We've got the full repertoire, Leon. It sounds ludicrous, I know, but whenever I'm thinking about alien life, the first place that occurs to me is planet Earth – the oceans, beneath the Earth's crust, the poles, the air. If you don't know your own planet, how can you get to grips with other worlds?'

'That's exactly our problem.'

They followed Peak further down the ramp. It linked the various levels like an enormous stairwell. The tunnel levelled out and turned into a passageway that led towards the stern. They were now at the heart of the Independence. A side-door had been left open, bathing the corridor in artificial light. As they walked in, Crowe recognised the biologist she'd spoken to via video link-up over the past few weeks. Sue Oliviera was standing beside one of a multitude of lab benches, talking to two men, who introduced themselves as Sigur Johanson and Mick Rubin.

The entire deck seemed to have been converted into a laboratory. Benches and equipment were grouped together like islands. Crowe noticed chest freezers and barrels of liquid. Two large containers had been joined together and were marked with biohazard signs; presumably the containment facility. In the middle was a structure the size of a small house, surrounded by a walkway. Steel ladders led up to the top. Thick pipes and bundles of cable connected the walls to box-shaped machinery. A large oval window revealed the diffusely lit interior. It seemed to be filled with water.

'You've got an aquarium on board?' said Crowe.

'A deep-sea simulation chamber,' explained Oliviera. 'The original's in Kiel. It's much bigger than this – but ours comes with a port-hole made of armoured glass. The pressure inside would kill you, but other organisms need it to survive. At the moment it's populated with several hundred white crabs that were caught in Washington and loaded into pressurised containers to be flown out here. It's the first time we've succeeded in keeping the jelly alive – at least, we think we have. We haven't caught sight of it yet, but we're sure it's lurking inside those crabs and controlling their movements.'

'Fascinating,' said Crowe. 'But I don't suppose the chamber's only here for the crabs, is it?'

Johanson flashed her an enigmatic smile. 'Who knows what'll turn up next in our nets?'

'So it's a kind of PoW camp.'

Rubin laughed. 'That's a good one.'

Crowe glanced around. With the exception of the door, the laboratory was sealed. 'Isn't this usually a vehicle deck?' she asked.

'Yes,' Peak told her. 'On the other side of this bulkhead is the stern half of the vessel with the hangar bay above us. You've read up on it, haven't you?'

I'm inquisitive, that's all,' Crowe said modestly.

'Well, let's hope your inquisitiveness translates into results.'

'What a grouch,' Crowe whispered to Anawak, as they left the lab.

'Oh, Sal's a decent enough guy. He's just not accustomed to know-it-all civilians.'

THE PASSAGEWAY ENDED in a hall, whose height and length exceeded the dimensions of even the hangar bay. They walked over an artificial embankment that sloped down towards a basin whose inset floor was lined with wooden planking. It looked like a vast empty swimming-pool. At its centre, the planks had been cut away to make room for an inverted glass structure made of two square flaps that sloped downwards, coming together to form an upside-down turret jutting out beneath the deck. Next to that was an enormous raised tank filled with water. Its rippling surface reflected the beam of the overhead lighting. Crowe saw slim, torpedo-shaped bodies gliding beneath the waves. 'Dolphins!' she exclaimed.

'Yes.' Peak nodded. 'Our marine mammal fleet.'

Her eyes shifted upwards. The monorail system covered the ceiling here too, the track branching off in several directions. Futuristic vehicles were suspended from above, like giant sports cars bred from submersibles and planes. On either side of the basin the embankment continued in the form of jetty-like walkways. Boxes of equipment and other goods were stacked along the walls. Crowe noticed probes, gauges and diving-suits hanging up in lockers. Ladders led down into the basin at regular intervals.

Four Zodiacs were resting on the wooden planking at the near edge of the basin.

'Someone pulled the plug, huh?'

'Yesterday evening. It's down there, by the way.' Peak pointed to the glass structure. Crowe tried to gauge its size – it had to measure at least eight by ten metres. 'That's our sluice gate, the entrance to the ocean – with a twin set of locks: glass flaps at the base of the pool and steel flaps in the hull. There's a three-metre vertical shaft between them. It's foolproof – the gates never open simultaneously. As soon as a submersible has been released into the shaft, we close the glass flaps and open the steel ones. When the sub returns, the same thing happens in reverse. The submersible enters the shaft, the steel flaps close, and we can peer through the glass to make sure there's nothing down there that shouldn't be. In the meantime, the water's being checked for chemicals – the shaft is lined with sensors that test it for impurities and toxins. The results appear on two displays, one near the glass flaps and the other on the control panel. The sub stays in the shaft for about a minute. The glass flaps won't open until we've received the all-clear, then it's released into the basin. We use the same procedure for the dolphins. Follow me.'

They walked along the starboard jetty. A console towered up from the decking, positioned at the edge of the pool and equipped with monitors and other gadgets. A bony man with piercing eyes and a handlebar moustache left the group of soldiers and came towards them. 'Commander Luther Roscovitz,' Peak introduced him. 'He's in charge of the dive station.'

'You're Ms Alien, right?' Roscovitz flashed his long, yellowed teeth in a grin. 'Welcome aboard for the cruise. What took you so long?'

'My spaceship was delayed. Neat desk.'

'It does the job. We use it to operate the hatches and for sending down the submersibles. It also controls the pump, for when we want to fill the basin.'

Crowe remembered what she'd read about the Independence. She jerked her head in the direction of the steel bulkhead that sealed the stern-side of the hall. 'That's a hatch too, isn't it?'

'A stern gate. By flooding the ballast tanks we can get the vessel to sit lower in the water, so when the stern gate's open, seawater rushes in and creates a nice little harbour with its own private entrance.'

'Cute place to work. I like it.'

'Oh, don't get me wrong. Normally this place is full of landing-craft, heavy-duty tugs and hovercraft. It's a big hall, sure, but in no time at all they're crammed in like sardines. We had to shift everything around for this mission. It was clear from the start that we wouldn't need landing-craft. All we were looking for was a ship heavy enough not to be sunk by any kind of sea monster, that could stand up to huge waves, and had all the latest in communications technology. Oh, and it had to have aircraft landing points and a dive station. It was lucky as hell that the LHD-8 was already in construction, the biggest and most powerful amphibious-assault vessel of all time. It was practically ready, but we had the option of making some changes. What more could you ask for? The shipbuilders in Mississippi are seriously good. They came up with a new design for the well deck, added the sluice system and modified the workings of the pump. Now we can flood the basin without using the stern gate. In fact, we'd only ever need to open it if we wanted to launch the Zodiacs.'