He called up a picture of an octopus, whose skin was covered with iridescent blue rings.

'Next up, Hapalochlaena maculosa, the blue-ringed octopus. Twenty centimetres in length, found in Australia, New Guinea and the Solomon Islands. One of the most poisonous animals in the world. Injects toxic enzymes with its bite. Its victims barely feel a thing, but in less than two hours they're stone dead.' Some of the organisms in the pictures were bizarre. 'Stone fish, weever fish, scorpion fish, bearded fireworms, cone snails – the seas are full of poisonous creatures like these. Usually the toxins are used for defence, but the number of incidents involving poisoning has increased significantly. In the case of some animals the statistics have shot through the roof, and there's a simple explanation: species that normally camouflage themselves and hide from humans have started to attack.'

Roche leaned towards Johanson. 'The question is, could something that triggers a change in a shark trigger a change in a crustacean?' Li heard him whisper. Is that possible?'

'I'd say it's deadly certain,' Johanson replied.

PEAK HAD MOVED on to the jellyfish invasion of coastal areas, which was reaching crisis proportions in South America, Australia and Indonesia. Johanson listened, with half-closed eyes. Portuguese men-of-war had started to release a toxin that could kill within seconds.

'For the sake of clarity we've split the phenomena into three different categories,' Peak said. 'Behavioural changes, mutations and environmental disasters. They're all interlinked, of course. So far we've looked at abnormal behaviour, but in the case of the jellies, we're dealing mainly with mutations. Box jellyfish have always been capable of navigation, but now they're real experts. You get the sense that they're patrolling. It's as though they're trying to clear the area of any human presence, even though we could never really harm them. The diving industry is on its last legs, but the fishermen are the real victims.'

The screen filled with a picture of factory trawler, a colossal vessel with an on-board facility that processed the catch.

'This is the Anthanea. A fortnight ago its crew caught a load of Chironex fleckeri. Box jellies, in other words. Or at least we think they're Chironex or something very similar. In any case, the fishermen made the mistake of not throwing them straight back into the water. Instead they opened the nets, and several tonnes of poison landed on the deck. Some fishermen were killed outright, others died later when the metre-long, practically invisible tentacles were scattered around the ship. It rained that day. The whole boat was awash with jellyfish remnants. No one knows how the toxin entered the drinking water, but the Anthanea became a ghost ship. Now people are warier, and the trawlers carry protective clothing, but the essential problem remains. Throughout much of the world, the fishing flotillas are catching poison, not fish.'

They're not catching fish because there aren't any left, thought Johanson. Come on, Peak, a detail like that deserves to he mentioned, even if it's not the real cause.

Or was it?

Of course it was. It was one of countless causes.

His mind switched to the worms.

All those mutant organisms that suddenly seemed to know what they were doing. Didn't anyone see what was happening? They were experiencing the symptoms of a disease whose pathogens were everywhere, but always in hiding. It was an amazing piece of camouflage. Man had emptied the seas of fish, and now the few remaining shoals had learned to avoid the death traps, while armies of poison-toting soldiers took their place in the nets, holding the ailing fishing industry in a toxic embrace.

The sea was killing mankind.

And you killed Tina Lund, Johanson thought somberly. You encouraged her not to give up on Kare Sverdrup. She listened to you, or she would never have driven to Sveggesundet.

Was it his fault?

How could he have known what would happen? Lund would probably have died in Stavanger too. What if he had told her to take the next plane to Hawaii or Florence? Would he be congratulating himself on having saved her?

They all had their personal demons to fight. Bohrmann was tormented by the notion that he should have warned the world earlier. Well, of course he should. But what would he have said? That he thought a catastrophe might happen? That one day, some time, disaster might strike? They'd pulled out all the stops to find a definitive answer. In the end they hadn't been fast enough, but at least they'd tried. Was Bohrmann at fault?

And what about Statoil? Finn Skaugen was dead. He'd been called to Stavanger docks just before the wave rolled in. Johanson was starting to see the oil boss in a different light. Skaugen had been a manipulator. All that guff about being the good conscience of an evil industry, but what had he done? Clifford Stone had also died in the catastrophe. Maybe he hadn't been the calculating monster that Skaugen had made him out to be.

Worms, jellies, whales, sharks.

Fish that could plan. Alliances. Strategies.

Johanson thought of his flattened house in Trondheim. It was odd, but he didn't feel too saddened by its loss. His real home was elsewhere, on the edge of a watery mirror that on clear nights contained the universe. He had caught sight of himself there, and created a haven for everything that was beautiful and true. The house was his creation, an embodiment of himself It was a refuge, in the way that a rented town-house could never be a home.

He hadn't been there since the weekend with Tina.

Would it have changed too?

The water in the lake was safe, but the thought of it made him uneasy. At the first opportunity he'd drive there and check up on it, no matter how much work the future held in store.

PEAK CALLED UP another image. The remains of a lobster.

'Hollywood would call it a messenger of doom or something,' said Peak, with a wry grin. 'And, in this case, the hype would be justified. Central Europe has been seized by an epidemic whose pathogens are hidden in creatures like these. Thanks to Dr Roche, we've now got the lowdown on the microscopic stowaways. The nearest taxonomical match is Pfiesteria piscicida, a single-cell alga. It's one of around sixty species of dinoflagellate that are known to be toxic. Of all the killer algae, Pfiesteria is the worst. Some years ago we had a nasty brush with it along the east coast of America, mainly in North Carolina. Pfiesteria was responsible for killing billions of fish. For the local fishermen it was an economic disaster, but it also affected their health. Many developed lesions on their arms and legs, suffered memory loss and eventually had to give up their jobs. Scientists researching Pfiesteria also experienced long-term health problems.' He paused. 'In 1990 one of the scientists investigating the algae, Howard Glasgow, was cleaning a glass tank in a specially designed lab at the University of North Carolina, when he noticed something was wrong. His mind was whirring, but his body seemed to move in slow motion. His limbs refused to keep up. Glasgow's illness was the first sign that the Pfiesteria toxins could get into the air, so the organisms were moved to a more secure facility. Unfortunately the building contractor had messed up, and the air vent pumped the toxins directly into Glasgow's office. No one noticed the mistake, so for the next six months he breathed toxic air. His headaches got so bad that he could barely work. He lost his balance. His liver and kidneys were poisoned. He'd speak on the phone and five minutes later all memory of the conversation would he gone. He wandered around town and lost his way home. He forgot his phone number and even his name. Most people were convinced that he had a brain tumour or was suffering from Alzheimer's, but Glasgow wouldn't listen. In the end he agreed to undergo a series of tests at Duke University, which showed that the problem was of a different nature. Other researchers who had come into contact with Pfiesteria later succumbed to lung infections and chronic bronchitis. And, slowly but surely, they lost their memory to an organism that defies our understanding.'