'But how will they exploit the methane?' asked Johanson. 'Won't the hydrates dissociate on the way to the surface?'

'That's where remote-controlled processors enter the equation. If you get the hydrates to dissociate while they're down there, by heating them, for example, all you've got to do is trap the gas and channel it to the surface. It sounds great, but who's to say that an operation like that won't start a chain reaction and trigger a heatwave like the one in the Paleocene?'

'Do you think that's possible?'

Bohrmann spread his hands. 'Every time we tamper with our environment without knowing what we're doing, we're dicing with death. But it's started already. The gas hydrate programmes in India, Japan and China are already quite advanced.' He gave a bleak smile. 'But they don't know what's down there either.'

'Worms,' murmured Johanson. He thought of the video images that Victor had taken of the seething mass on the seabed. And of the ominous creature that had disappeared into the dark.

Worms. Monsters. Methane. Natural disasters.

It was time for a drink.

Vancouver Island and Clayoquot Sound, Canada

The sight of it made Anawak angry. From head to fluke it measured over ten metres, an enormous male orca, one of the biggest transients he had ever seen. Its half-open jaws revealed tightly packed rows of glistening conical teeth. The whale was past its prime, but still immensely powerful. It wasn't until Anawak examined it more closely that he noticed the dull, worn patches that flecked its shiny black skin. One of its eyes was closed and the other was hidden from view.

Anawak had recognised it straight away. On the database it was listed as J-19, but its distinctive dorsal fin, curved in the shape of a scimitar, had earned it its nickname: Genghis. He walked to the other side of the body and spotted John Ford, director of Vancouver Aquarium's marine-mammal research programme, talking to Sue Oliviera, head of the lab in Nanaimo, and another man. They were gathered under the line of trees that fringed the beach. Ford beckoned Anawak over. 'Dr Ray Fenwick from the Canadian Institute of Ocean Sciences and Fisheries,' he said.

Fenwick was there for the autopsy. As soon as they'd heard that Genghis was dead, Ford had suggested that the dissection should be conducted on the beach, where the carcass had been found, rather than behind closed doors. He wanted to drum up a large group of students and journalists and give them an insight into the orca's anatomy. 'Besides,' he'd said, 'the autopsy will look different in the open – less clinical and distant. We'll be staring at the corpse of an orca close to the sea – in its own world. People will be more involved, more compassionate. It's a gimmick, of course, but it'll work.'

They'd thrashed it out between them: Ford, Fenwick, Anawak and Rod Palm, a naturalist from the marine research station on Strawberry Isle, off the coast of Tofino. Palm and the Strawberry Isle team monitored the ecosystem in Clayoquot Sound, and Palm had made a name for himself by studying the orcas there.

'The external evidence suggests that it succumbed to a bacteriological infection,' said Fenwick, when Anawak pressed him, 'but I don't want to rush to any hasty conclusions.'

'You don't have to,' said Anawak grimly. 'Remember 1999? Seven dead orcas, and all of them infected.'

"The Torture Never Stops",' murmured Oliviera, recalling an old Frank Zappa song. She nodded conspiratorially at Anawak. 'Come with me a second.'

Anawak followed her over to the carcass. Two large metallic cases and a container had been placed beside it, full of tools for the autopsy. Dissecting an orca was a different matter from dissecting a human. It meant hard work, vast quantities of blood and one hell of a stench.

'The press will be here in a moment, with the students,' she said, glancing at her watch, 'but since we're together, we should have a word about those samples.'

'Made any headway?'

'Some.'

'And you're keeping Inglewood in the picture?'

'I thought you and I should talk first.'

'Sounds like you haven't reached any firm conclusions.'

'Put it this way, we're amazed on one count and stumped on the other,' said Oliviera. 'For one thing, the mussels aren't described in any of the existing research.'

'I could have sworn they were zebras.'

'On the one hand, yes, but on the other, no.'

'Fill me in.'

'There are two ways of looking at it. We're either dealing with a species related to the zebra mussel or with a mutation. They look like zebra mussels and they form colonies like zebra mussels, but there's something odd about the byssus. The fibres extending from the foot are unusually thick and long. We've nicknamed them "jet mussels".' She pulled a face. 'We couldn't come up with anything better. We've observed a number of living specimens, and they're able to. . . Well, they don't just drift like normal zebra mussels. They set their course by sucking in water and expelling it. The force drives them forwards, and they use their fibres to steer. Does that remind you of something?'

'Squid use jet propulsion.'

'Well, some species do, but there's something else. I was thinking of dinoflagellates, unicellular organisms. In certain species, the cells have a pair of flagella extending outwards from the cell wall. They use one flagellum to steer, while the other rotates, moving them forward.'

'But apart from that they've got nothing in common.'

I'm treating it as convergent evolution in a very broad sense. At this stage, I need every lead I can get. As far as I know, no other species of mussel moves around like that. These swim like shoaling fish, and they can keep up their momentum, in spite of the weight of their shells.'

'Well, that would explain how they settled on the Barrier Querns hull in the middle of the ocean,' mused Anawak. 'Is that the amazing part?'

'Right.'

'What's stumped you?'

Oliviera stepped closer to the dead whale and stroked its skin. 'The fragments of tissue you found down there. We don't know what to do with them – and there's not much we can do. For the most part it had already decomposed. The small amount that we were able to analyse seemed to indicate that the substance on the propeller and the substance on your knife were identical. Apart from that, it bore no resemblance to anything we've ever come across before. The tissue is unusually well developed in terms of its contractibility. It's incredibly strong, but also extremely elastic. We don't know what it is.'

'Could that be an indication of bioluminescence?'

'Possibly. Why?'

'Because it flashed at me.'

'You're talking about the thing that knocked you over?'

'Yeah. It shot out while I was poking around in the mussel bed.'

'Maybe because you'd cut a lump out of it. Although I can't believe this tissue contains nerve fibres or anything else that might make it feel pain. It's really just… cell mass.'

They heard voices approaching. Across the sand, a group of people were heading towards them, some with cameras, others with notepads.

'We're on,' said Anawak.

'OK.' Oliviera looked at him helplessly. 'But what do you want me to do? Should I forward the results to Inglewood? I can't imagine they'll be of any use. I'd rather look at a few more samples – especially of that tissue.'

'I'll get in touch with Roberts.' Anawak stared at the orca, depressed.

First the whales had disappeared for weeks, and now there was another corpse. 'Why did this have to happen? It's such a mess.'

Oliviera shrugged. 'Save your lamentations for the press,' she said.

THE AUTOPSY TOOK MORE than an hour, during which Fenwick, assisted by Ford, cut open the whale and explained its anatomical structure, exposing its intestines, heart, liver and lungs. Its stomach revealed a half-digested seal. Unlike the resident orcas, transient and offshore orcas ate sea-lions, porpoises and dolphins – even baleen whales could fall prey to a pod of orcas.