There was a flash.

A cry went up from the deck.

In a split second the scene had changed. Lightning zigzagged through the water, branching out between the swirling eddies. A mute storm raged beneath the surface of the sea. Then the maelstrom retreated, peeling back from the vessel's hull, as the blue cloud rushed towards the horizon, disappearing at breathtaking speed.

Greywolf ran towards the island.

'Jack, wait!' Delaware darted after him. The others followed. He hurried through the vessel, swinging down the companionways, then striding through the command centre and bursting into the CIC, Peak and Li close behind him. The cameras on the hull showed nothing but dark green water. Two dolphins swam into view.

'What's going on?' Peak called to the guys at the monitors. 'What are you getting from the sonar?'

A man swivelled round. 'There's something big out there, sir. Something – well, it's uh, kind of-'

'Kind of what?' Li grabbed his shoulder. 'We need information, you moron. What's happening?'

The man blanched. 'It's – it's- First there was nothing on the screen, then the next second there were sheets of something. They came out of nowhere. The sea just went solid. They turned themselves into a wall or something, they were – they were everywhere.'

'Dispatch the Cobras. I need them up there now, surveying the area.'

'What are the dolphins reporting?' asked Greywolf.

'Unknown life-form,' said a soldier. 'The dolphins detected it first.'

'Is it localised?'

'No, everywhere. But it seems to be retreating – one kilometre and still moving. The sonar's showing vast swathes of something all around the ship.'

'Where are the dolphins now?'

'Underneath us. They're crowding in front of the hatch. I think they're scared. They want to come in.'

People were still pouring into the GIG.

'Bring up the satellite footage,' commanded Peak.

The enormous monitor mounted at the head of the room showed the Independence, as seen by KH-12. She was resting on a dark expanse of water. There was no trace of any blue light.

'Just now the whole screen was lit up,' said the guy in charge of monitoring the satellite feedback.

'Any other satellites we can look at?'

'Nothing available, sir.'

'Zoom out on KH-12, then.'

The man relayed the command to the control centre. A few seconds later the Independence dwindled on the screen and the Greenland Sea extended across it. Whistles and clicks came through the speakers, as the dolphins continued to issue their warning of the unknown presence below.

'Keep going.'

KH-12 zoomed out further. It was now covering a hundred square kilometres. The Independence was 250 metres long, but now it looked like driftwood. They stared at the monitor with bated breath.

And then they saw it.

A thin blue glow was stretched in a vast ring round the vessel. It quivered with flashes of light.

'How big is it?' asked Peak, in a whisper.

'Four kilometres in diameter,' said the woman in front of the screen. 'No, it's bigger. It's some kind of funnel. The image that we can see here is only the opening. The whole thing stretches into the depths. And we're, uh… suspended over its jaws.'

'What's it made of?'

Johanson had appeared in the room next to Peak. 'Jelly, I should think.'

'Congratulations,' wheezed Vanderbilt 'What the hell did you send them?' he snarled at Crowe.

'We asked them to show themselves.'

'Was that wise?'

Shankar spun round angrily. 'We're supposed to be making contact, aren't we? What the hell is your problem? Don't tell me you were expecting messengers on horseback-'

'We've got a signal!'

They swivelled in the direction of the voice – it was the guy in charge of acoustic surveillance. Shankar was there in an instant. He bent over the screen.

'What is it?' Crowe called.

'From the look of the spectrogram, I'd say it was a Scratch signal.'

'An answer?'

'I don't know whether-'

'The ring! Look, it's contracting.'

Their heads jerked towards the main screen. The ring of light was creeping back slowly towards the ship. At the same time, two tiny dots sped away from her. The Cobras had started their recce. The whistling and squeaking from the speakers grew louder.

Suddenly they were all talking at once.

'Quiet!' barked Li. Her forehead creased as she listened to the dolphins. 'They've changed their signal.'

'Yes.' Delaware closed her eyes in concentration. 'Unknown creatures and…'

'Orcas!' cried Greywolf before she could finish.

'We've picked up a number of large animals approaching from below,' said a member of the sonar team. 'They're inside the tube.'

Greywolf turned to Li. 'I don't like the sound of this. We should bring the dolphins inside.'

'Why now?'

I'm not prepared to put their lives at risk. And, anyway, we need the footage from their cameras.'

Li hesitated for a moment. Then she made up her mind. 'OK. Fetch them in. I'll tell Roscovitz. Peak, go with him. Take four of your men.'

'Leon?' said Greywolf 'Licia?'

They hurried out. Rubin watched them go. He leaned towards Li and said something in a low voice. She listened, nodded and turned back to the screens. 'Wait for me!' Rubin yelled. I'm coming too.'

WELL DECK

Roscovitz, Browning and one of her technicians reached the well deck before the scientists arrived. The commander swore when he saw the broken-down Deepflight. It was floating on the surface with the pods flipped open, tethered by a single chain that stretched up to the rail overhead. 'I thought I told you to finish the job,' he snapped at Browning.

'It's more complicated than we thought,' the head technician protested, as they strode along the jetty. 'The steering system is-'

'Shit.' Roscovitz stared at the submersible. It was positioned half-way over the sluice, whose contours were partially visible in the water, four metres below. 'I don't like it there, Browning. And I especially don't like it there when we're letting the dolphins in and out.'

'With all due respect, sir, it's not in the way. Just as soon as we've repaired it, we'll hoist it back on to the rail.'

Roscovitz growled incomprehensibly and took his position at the controls. The boat was lying in front of him. From that angle it blocked his view of the sluice. He'd have to rely on the footage on the screens. He swore again, this time using juicier expressions. The Independence had been equipped in great haste – shoddily, it seemed. If things weren't going to work properly, why the hell didn't they cause problems before they were in use? What was the point of testing every last piece of hardware if his view would be blocked by a floating submersible?

Steps echoed through the hangar deck. Greywolf, Delaware, Anawak and Rubin hurried down the ramp, followed by Peak and his men. The soldiers spread out on either side of the jetty. Rubin and Peak headed towards Roscovitz while the others pulled on their wetsuits and adjusted their masks.

'Ready,' said Greywolf. He made the OK sign, forming a circle with his forefinger and thumb. 'Let's bring them in.'

Roscovitz switched on the audio recording to summon the dolphins. He saw the scientists splash down into the basin, their bodies illuminated by the underwater lights. They swam towards the sluice. One by one they dived towards the glass hatch. He opened the flaps in the hull.

DELAWARE SANK HEAD FIRST towards the display panel beside the hatch. She was still diving when the enormous steel plates jolted into action, three metres below the inverted glass turret. She watched as they swung open to reveal the water below. Two dolphins slid into the sluice. They seemed nervous, pressing their snouts against the glass. Greywolf signalled for them to wait. A third dolphin swam in.