They were powerless to help. The death toll kept rising, and there was nothing they could do to stop it. The OEM had published reams of regulations and recommendations, but the steady stream of warnings and drills had been in vain. Every household had been instructed to keep a canister of drinking water at the ready, in case of an emergency, but no-one was prepared. In any case, a safe supply of drinking water couldn't protect people against the toxins rising from drains or wafting up from washbasins, toilets and dishwashers. All Peak could do was herd those who were still in good health out of the danger zone and quarantine them in vast camps. New York's schools, churches and other public buildings now served as hospitals, and the belt of land surrounding the city was an enormous jailhouse.

He looked to the right. The fire was still blazing in the tunnel. The driver of a military tanker had failed to follow the protocol for securing his gas mask, and had lost consciousness at the wheel. He'd been part of a convoy. The accident had set off a chain reaction: dozens of vehicles had burst into flames. Right now the temperature down there was equivalent to the heat inside a volcano.

Peak berated himself for not having prevented the accident. It was obvious that the danger of contamination would be many times higher inside a tunnel than on the streets, where the toxins could disperse. But how could he be everywhere at once?

If there was anything Peak hated, it was the feeling of powerlessness.

And now it was Washington's turn.

'We can't handle it,' he'd told Li on the phone.

'We have to.'

They crossed the Hudson River and made for Hackensack airport, where a military chopper was waiting to take Peak to Vancouver. They left the lights of Manhattan behind them. Peak thought of the scientists' meeting scheduled for the following day. Would they make any headway? He wished they could at least find a drug that would put an end to the horror in New York, but something told him not to get his hopes up.

Peak leaned back and closed his eyes.

CHATEAU WHISTLER, Canada

Li was pleased with herself. In view of the impending Armageddon, it would have been more appropriate to feel anguished or shocked, but the day had been a resounding success. Vanderbilt had been forced on to the defensive, and the President had listened to her advice. After countless telephone calls she now knew all the latest on the apocalypse, and was waiting impatiently to talk to the defense secretary. The sonar offensive would be starting the next day, and she wanted to discuss the deployment of boats. The defense secretary was caught up in a meeting, and wouldn't be able to talk for another few minutes.

It was approaching two o'clock in the morning when she sat down at the piano to play some Schubert. The telephone rang. She jumped up to answer it. She'd been expecting the Pentagon, so she was thrown by the voice on the line. 'Dr Johanson! What can I do for you?'

'Have you got a moment?'

'Now?'

'I'd like to speak to you in private.'

'I'm afraid I'm busy. How about in an hour? I need to make some calls.'

'Aren't you curious?'

'Curious?'

'You said you thought I had a theory.'

'Come up to my suite.'

With a smile she replaced the receiver. It was exactly as she had expected. Johanson wasn't the type to use every last second of a deadline, and he was too well mannered to go back on his word. He had wanted to be the one to decide when he told her, and he'd chosen the middle of the night.

She called the Pentagon switchboard. 'Postpone my teleconference with the defense secretary by half an hour.' She changed her mind. 'Make that an hour.'

Johanson was bound to have plenty to say.

VANCOUVER ISLAND

Anawak didn't have much of an appetite after Greywolf's explanations, but Shoemaker had excelled himself. He'd fried some steaks and concocted an impressive salad, topped with croutons and nuts. They ate on the veranda. Delaware was careful not to mention her budding relationship, and she was excellent company. She had an inexhaustible supply of jokes, and delivered even the corniest with perfect timing.

The evening was an oasis in a sea of misery.

During the Dark Ages, people had danced and caroused in the streets of Europe while the Black Death raged round them. Although there was no dancing or singing at Shoemaker's, they talked for several hours without a word about tsunamis, whales or killer algae. Shoemaker told anecdotes about the early days at the Station, and they enjoyed the balmy evening. Relaxing on the veranda, they gazed out over the dark waters of the bay.

Anawak left at two in the morning, but Delaware stayed behind. She and Shoemaker were deep in conversation about old movies and had just cracked open another bottle of wine. They were descending into tipsiness, so Anawak made his way through the night air to the station. He switched on the computer and went online.

Within minutes his search for Professor Kurzweil was rewarded.

As dawn broke, a picture began to emerge

12 May

Chateau Whistler, Canada

Maybe, thought Johanson, this will be the turning-point. Or maybe they'll think I'm a crazy old fool.

He was standing on the little dais to the left of the screen. The projector was switched off. There'd been a few minutes' delay as they waited for Anawak, who'd stayed the night in Tofino, but now the delegates were assembled. The front row was occupied by Peak, Vanderbilt and Li. Peak had returned overnight from New York, and looked as though he'd left most of his energy there.

Addressing an audience was second nature to Johanson. He was used to lecturing students and speaking at conferences, occasionally adding his own insights and hypotheses to the standard set of facts. But for the most part standing at a lectern was the easiest thing in the world: you merely imparted the fruits of other people's research, and answered questions at the end.

Yet this morning he was experiencing the unfamiliar sensation of self-doubt. How on earth could he put across his theory without his audience laughing in his face? Li had conceded that he might be right, so he'd stayed up most of the night, drafting and redrafting his speech. Johanson had no illusions. He was only going to get one shot at this: either he won them over with a surprise attack, or they decided he was nuts.

He glanced at the top page of his print-out. He'd written a detailed introduction. Now, after three hours' sleep, it suddenly struck him as impenetrably complicated. He'd been satisfied with it in the early hours of the morning, when he was almost too exhausted to think, but now…

He laid aside his notes, and felt relieved of a burden. His self-assurance returned to him like a cavalry ready for battle, flags flying and trumpets blaring. He took a step forward and, once he was sure he had his audience's attention, he said, 'It's very simple, really. Dealing with the implications will be tricky, but the basic principle is logical and straightforward. We're not dealing with a series of natural disasters. And we're not doing battle with any terrorist organisation or rogue state. Not even evolution is to blame.' He paused. 'No. What we're experiencing is the fabled war of the worlds – a war between two worlds that we've always thought of as one because they're bound together. All this time we've been gazing upwards in anticipation of an alien species arriving from space, when intelligent life-forms have been with us all along, inhabiting part of the planet that we've never seriously attempted to explore. Two radically different systems of intelligent life coexist on the Earth, and they've done so peacefully until now. While one has been observing the development of the other since time immemorial, the other has no concept of the complexity of the underwater world – or, if you like, the alien universe sharing our globe. Outer space is on Earth, in the oceans. We've found our extraterrestrials, and they don't come from faraway galaxies. They evolved at the bottom of the sea. Life in the water existed long before the first organisms appeared on land, and this species is likely to be far, far older than humanity. I can't tell you what these creatures look like, or how they live, think or communicate. But we're going to have to get used to the notion that we're not the only smart species on this planet. For decades we've been systematically destroying the habitat of another intelligent race – and now, ladies and gentlemen, these creatures seem justifiably irate.'