Ford reached to one side, keeping his eyes on the screens, and stuck his hand into a carton. A handful of congealed chips disappeared into his mouth.

Lucy didn't give the impression that she was rampaging.

Over the past few hours she'd been doing what benthic feeders did best – grazing, with half a dozen adult greys and two adolescents. At regular intervals she'd pushed her way through curtains of seaweed towards the bottom, raising clouds of sediment as she ploughed through sandy silt, catching worms and amphipods. Lying on her side, she'd tilled long furrows with her narrow bow-shaped head. In the beginning he'd been fascinated. It wasn't the first time he'd seen pictures of grey whales feeding, but the URA swam with the pod. Its footage was in a different league. He could even see much of the detail. Following a sperm whale to its feeding grounds would have meant sinking to the depths of the ocean, but grey whales loved the shallows. So for hours Ford had been watching an alternating picture of light and dusk. Lucy bobbed along the surface for a few minutes, filtered out the silt through her baleen, filled her lungs with air, then returned to the bottom. She came so close to the shore that most of the pictures had been taken at depths of less than thirty metres.

Ford watched as the scarred and mottled body slid over the sediment, swirling up the silt. 'The robot found it easy to follow the whales because they barely left the spot, swimming just a few metres in one direction, then a short distance in the other, shuttling back and forth, up and down, feeding, returning to the surface and plunging under water. Ford liked to compare Vancouver Island to a service station where whales hung out and snacked – which was what the pod was doing now.

Up to the surface, down to the sea floor, feeding, swimming.

After a while it got boring.

At one point a group of orcas appeared in the distance, but it didn't stick around. Most of the time, encounters like that passed without incident, although orcas were the only creatures apart from humans to prey on large whales. Not even blue whales were safe. When orcas went for the kill, it was a ferocious group attack. They took bites of their victim's lips and tongue, leaving behind a gigantic, mutilated corpse that sank slowly to the bottom.

Down to the sea floor, up to the surface, diving, feeding.

Lucy fell asleep. At least Ford assumed that she was sleeping. With his assistants he watched the picture darken, as daylight aimed to dusk. A shadow was visible against the black background: Lucy's body, suspended upright in the water, sinking slowly towards the bottom, then creeping up again. Several marine mammals rested in that way. Every few minutes they rose to the surface in their half-sleep, breathed and sank down, still slumbering. Remarkably, they never slept longer than five or six minutes at a time, yet the short naps added up to a rest.

Eventually the screens went black. Only the green lights betrayed the position of the pack.

It was night.

Nothing to see, still he had to watch – the tedium was hard to bear. Now and then something flashed across the screen; a jellyfish or a squid. Otherwise it was blacker than black. A stream of data continued to flow across the second monitor – details of Lucy's metabolism and her physical surroundings. The green lights moved lethargically through the virtual space. Not all of the animals in the pod would sleep at night. Whales slept irregularly, at different times of day or night. From the screen he could tell that Lucy and the other greys had stopped diving and feeding. From time to time the temperature changed by half a degree, depending on the depth. Everything else stayed constant. The grey whale's heart was beating steadily, sometimes speeding up a little, sometimes slowing down. The URA's hydrophone picked up all kinds of underwater noise: swooshing and bubbling, orca calls and the song of the humpbacks, bellowing and growling, the distant whir of a ship's propeller, but nothing out of the ordinary.

Ford sat in front of the pitch-black screen and yawned until his jaw clicked.

He gathered up the last few chips. His fingers stiffened. He squinted at the screen. Something was happening to the data.

From the moment the probe had started to record, it had registered a depth of between nought and thirty metres. Now it was registering forty, then fifty. Lucy was on the move. She was swimming towards the open sea and diving deeper all the time. The other whales followed rapidly. There was no hanging about now. This was migration speed.

What's the hurry? thought Ford.

Lucy's heartrate slowed. She was still diving, gliding rapidly downwards. Now her lungs would contain only ten per cent of the oxygen she was carrying, maybe less. The rest was stored in her blood and muscles.

Lucy was over a hundred metres below the surface. The blood supply to her non-vital body parts had already shut down. A tangled network of capillaries absorbed the diverted blood. Muscle movement and metabolism proceeded anaerobically. Over millions of years a series of astonishing changes had enabled the former land-dwellers to move effortlessly between the surface and the depths; to most fish, a change in pressure of just a hundred metres posed mortal danger. Lucy continued to sink, 150 metres, 200, moving steadily from the shore.

'Bill? Jackie?' Ford called. His eyes were fixed on the screen. 'Come and look at this.'

They crowded round the monitors.

'She's diving.'

'At a fair pace, too. She's three kilometres from the shore already. The whole pod's heading out to sea.'

'Maybe it's time for them to get going again.'

'But why would they dive so deep?'

'Plankton sinks at night, doesn't it?

'No.' Ford shook his head. 'That makes sense for other species, but not for benthic feeders. They've got no reason to-'

'Look! Three hundred metres.'

Ford leaned back. Grey whales weren't especially fast. If need be, they could put on a spurt, but ten kilometres an hour was as fast as they usually travelled, unless they were migrating or fleeing from a predator.

What had got into them?

He was sure now that he was observing anomalous behaviour. Grey whales fed almost exclusively on benthic organisms. When they migrated, they never strayed further than two kilometres from the coast. Ford wasn't sure how they'd cope at a depth of 300 metres. Ordinarily they never ventured below 120 metres.

Suddenly something lit up at the bottom edge of the grid: a green flash that shone for a moment before it was extinguished.

A spectrogram! The visual representation of a sound wave.

Then another.

'What was that?'

'Some kind of sound. The signal's pretty strong.'

Ford stopped the tape and rewound. They watched the sequence again. 'It's an incredibly loud signal,' he said. 'Like an explosion.'

'But there haven't been any explosions near here. We'd hear an explosion. This is infrasound.'

'I know. I only said it was like an explo-'

'There it is again!'

The green dots on the screen had stopped. The loud noise appeared a third time, then vanished.

'How deep are they?'

'Three hundred and sixty metres.'

'Unbelievable! What are they doing down there?'

Ford's gaze shifted to the left-hand screen, showing the footage from the camera. The black screen. His mouth dropped open. 'Look at that,' he whispered.

The screen wasn't black any more.

Vancouver Island

Frank's company was just what Anawak had needed. They had strolled along the beach towards the Wickaninnish Inn, discussing the environmental project with which Frank was involved. He came from a long line of fishermen, and now ran a restaurant, but recently the Tla-o-qui-aht had begun an initiative to combat the damage caused by logging. 'Salmon Coming Home' stood for their attempt to restore the complex ecosystem of Clayoquot Sound. The timber industry had devastated the area. No one was naive enough to think that the forest could be restored, but plenty could be done. Clear-cut logging was to blame for the forest floor drying out in the sun and washing away in the rain. The topsoil flushed into lakes and rivers, adding to the congestion caused by stones and abandoned timber and depriving the salmon of their spawning grounds. With its disappearance, an important food source had been lost to other animals. The restoration project helped to train volunteers to clear the rivers and cut a path through disused roads where water used to flow. Protective walls of organic debris were constructed along drainage channels, while the banks were planted with fast-growing alder. Slowly the environmentalists were restoring some of the balance to the relationship between forest, humans and animals. It took constant energy and drive, and there was little prospect of speedy results.