That was one of the reasons why energy experts at the end of the second millennium had got their predictions so badly wrong when they'd estimated that oil reserves would last for decades. Technically they were right: the Earth was drenched with oil. Yet most of it was inaccessible or the yield didn't justify the expense of extracting it.

At the beginning of the third millennium the dilemma provoked a ghoulish situation: OPEC, pronounced dead in the eighties, returned to life. Of course, it could do nothing to solve the real problem, but there was no doubt that it held the largest reserves. Determined not to let OPEC dictate the price of oil, the North Sea states had no choice but to lower the costs of extraction and colonise the seabed with automated plants. The ocean fought back with a brand new set of problems, starting with extremes of temperature and pressure. For whoever solved them, a second El Dorado beckoned. The riches wouldn't last forever, but in the meantime they would satisfy humanity's craving for oil and gas, and keep the industry alive.

Stone called in the experts, pushed the prototype through the test phase and recommended construction. Statoil acquiesced. Stone saw his budget and jurisdiction increase overnight. He cultivated his relationship with the suppliers, ensuring Statoil's needs always came first. He knew what a fine line he was treading. So long as no one had cause to criticise the company, he was Statoil's conquistador – but if it came to the crunch, he wouldn't stand a chance. The best employee was the easiest fall-guy. Stone knew he had to make it to the boardroom before anyone decided he was expendable. Once his name became synonymous with innovation and profit, doors would open and he'd be free to choose his path.

At least, that was how he'd imagined it.

He wasn't sure whom he felt angrier with – Skaugen, who'd betrayed him, or himself. But he'd known the score from the beginning, and the worst-case scenario had occurred. Everyone was dashing for shelter. Skaugen knew as well as he did that the catastrophic disintegration of the slope would soon be public news. None of them could afford to keep quiet without risking disgrace. By contacting the other companies, Statoil had set a process in motion that couldn't be stopped. Each firm was putting pressure on the next. With an environmental disaster looming, it was too late to strike a deal. All they could do was try to cover their own backs and find someone else to take the blame.

Stone seethed. Finn Skaugen was the biggest villain of them all – it had made Stone retch to see him play the good guy. His game was more treacherous than anything Stone, even in his darkest moments, could ever have devised. Of course Stone had overstepped his usual remit, but not without good reason. He was doing their bidding. He hadn't used half the power they'd given him. Of course he'd 'omitted' to mention those ridiculous reports. Since when had worms stopped ships taking to the water or oil being drilled? Every day thousands made their way through billions of planktonic organisms. If they stayed at home every time a new copepod was discovered, the oceans would be empty. And as for the hydrates – the amount of gas escaping was well within the normal limit. It was obvious what would have happened if he'd submitted the report. The bloody bureaucrats would have held up construction for no reason at all.

The system was to blame, Stone thought grimly, but most of all Skaugen, with his sickening brand of bigotry. All the directors, smiling and thumping him on the back; well done, old man, keep up the good work, just don't get caught, because we won't want to know. It wasn't his fault he was in this mess, it was theirs. And Tina Lund was just as bad, sucking up to Skaugen to take Stone's job and probably sleeping with the asshole too. Worst of all, he'd even had to pretend to be grateful to her for getting Skaugen to give him another chance. He was supposed to find the missing prototype. Some chance. It was a trap. They'd all turned against him, the whole bloody lot of them.

He'd show them, though. Clifford Stone wasn't finished yet. Whatever was wrong with the unit, he'd find the problem and sort it out. Then they could look for skeletons in the cupboard, and he, for one, had nothing to hide.

He'd get to the bottom of it.

The Thorvaldson had scanned the site of the unit with multibeam sonar, but there was still no sign of the processor. The morphology of the seabed seemed to have changed. Within a few days the site of the unit had become a gaping chasm. The thought of the depths made Stone as queasy as the next man, but he pushed aside his fears. All he could think of was his voyage to the seabed and how he'd show them what he was made of.

Clifford Stone, intrepid man of action.

On the afterdeck of the Thorvaldson the submersible was waiting to transport him to the seabed, nine hundred metres below. Of course he should have sent the robot down first on a recce. That's what Jean-Jacques Alban and all the others had been urging him to do. Victor was equipped with fantastic cameras, a highly sensitive articulated arm and every conceivable instrument necessary for the highspeed evaluation of data. But going down there himself would make more of an impression. In any case, Stone disagreed with Alban. He'd spoken to Gerhard Bohrmann on the Sonne about travelling on manned submersibles. Bohrmann had explored the Oregon seabed in Alvin, the legendary DSV: 'I've seen thousands of video images – footage recorded by robots, all of it very impressive – but actually sitting in the submersible, being-down there on the seabed, seeing it all in 3-D, I never thought it could be like that. It beats anything you've ever seen.' Besides, he'd added, there was no real substitute for the senses and instincts of a human.

Stone smiled grimly. It was his turn now. The submersible had been easy to get hold of, thanks to his excellent contacts. It was a DR 1002, a Deep Rover, made by the American firm Deep Ocean Engineering, a small, light boat, belonging to the new generation of submersibles. Its transparent spherical hull was mounted on bulky battery pods from which a pair of robotic arms emerged. Inside, there were two comfortable seats with controls to each side. As he approached the Deep Rover he felt pleased with his choice. The vehicle was attached to the boom by a cable, and had been jacked up to allow just enough room for them to crawl in through the bottom hatch. The pilot, Eddie, a stocky ex-navy aviator, was already inside, checking the instruments. There was the usual bustle before the launch of a submersible, with crew, technicians and scientists milling on the deck. Stone spotted Alban and called him over. 'Where's the photographer?' he shouted. 'And the guy with the video camera?'

'No idea,' said Alban. 'I saw the cameraman prowling around earlier.'

'Well, tell him to stop prowling and get here,' Stone snapped. 'We're not going under without this being filmed.'

Alban frowned and looked out to sea. It was a misty day with poor visibility.

'It smells bad,' he said.

'That's the methane.'

'It's getting worse.'

It was true. A sulphur-like odour hung over the sea. A good deal of gas must have escaped for the air to smell that bad. It didn't bode well.

'It'll sort itself out,' said Stone.

'I think you should postpone the dive.'

'Rubbish!' Stone glanced around. 'Where's that bloody photographer?'

'It's too risky – the barometer's plummeting. A storm's on its way.'

'We're going, and that's that.'

'Stone, don't be a fool. And, anyway, what's the point?'

'The point,' Stone said, in a hectoring tone, 'is to get a better, more accurate look at the problem. For God's sake, Jean, nothing'll get in the way of the Rover, least of all a few worms. It can descend to a depth of four thousand metres-'