'I only knew approximately. I wasn't the only one doing assays on that damned IGY ship, and I couldn't get at all the information I wanted.' His sullen tone implied that such information should have been his by rights, which was typical of him, but I was on the right track in getting him to talk about his own cleverness. Few genuine egotists can resist such an appeal.

'Who had the bright idea that found us here, then? We could have been anywhere. We could have been a hundred miles from here. You couldn't know where we were.'

He laughed. 'Couldn't I? Couldn't we? I know you like a book, Mike. I knew that you'd find that deposit given time to survey properly – so I gave you that time. And I knew that once you'd found it you couldn't resist investigating the source. I knew you'd have to come to Fonua Fo'ou, to Falcon.

Ramirez couldn't see it, of course. He can be a stupid man at times. But I convinced him that I knew my own brother. We've been hanging round here for two bloody weeks waiting for you to turn up.'

I said, 'How did you get tangled with Ramirez?' We already knew the answer to that one but it kept him talking.

'Campbell there couldn't finance me and Suarez-Navarro could. It was as simple as that. Who else should I go to but them? They'd just shown that they weren't too scrupulous by what they'd done to his mines, so they were just what I wanted.'

'And then they led you into murder. You had to kill Norgaard.'

'That was an accident,' said Mark irritably. 'All Sven was doing was tying up loose ends. We were waiting for the hue and cry to die down, and then Suarez-Navarro were going to provide us with a proper survey ship to find this stuff.' He thumped the papers and notebook. 'Meantime that damned fool decided that he wanted to publish. You see, he didn't know much about Suarez-Navarro and that's the way I wanted it. We had an argument – he was a pretty excitable chap – at first in words, and then it came to blows. The next thing I knew was that he'd cracked his head open on the coral. But I didn't mean to kill him, Mike. I swear it. All I ever wanted to do was to shut him up.'

'All you ever want to do is to shut people up,' I said flatly. 'How do you go about shutting up a good scientist, Mark? It seems to me that the only way is to kill him.'

I was cold inside, chilled by his amoral egocentricity. Everything he had done was justified in his own eyes, and everything that had gone wrong was the fault of other people.

Mark waved me aside. 'Hadley knew, of course. He was my liaison with Ramirez. They helped me to cover it up, but somehow the police got onto it.'

'My God, you think I'm naive,' I said. 'Look, Mark, I wouldn't be surprised if Ramirez didn't tip off the police himself. It wouldn't matter to him – he was in the clear. He arranged for your "death" and that was that. But he had you neatly wrapped in a package from then on, and you couldn't do a thing without his say so.'

'It wasn't like that,' Mark muttered.

'Wasn't it? Even when the first plan went wrong and Hadley was implicated in your so-called murder Ramirez wasn't worried. That's why he laughed his damn head off when I accused him. He knew that all he ever had to do to clear himself and Hadley was to produce you, and you can be sure he'd do it in such a way that would earn. him the congratulations of the law.'

'What do you mean by that?'

'He'd produce you dead – or dying, Mark – just so you couldn't talk. And the police would pat him on the back for capturing Mark Trevelyan, the murderer of Sven Norgaard, and maybe the mastermind behind the killing of Schouten. By God, I was right when I called you stupid. You'd really got in over your head, hadn't you?'

He was angry and baffled, and I could see that my attack had hit home; doubt was in his every action.

Campbell said, 'It doesn't make any difference now. Mark, you're for the deep six along with the rest of us. Ramirez will see to that.'

Geordie laughed without humour. 'Do you think you can trust Ramirez?'

Mark thought deeply and then shook his head. 'Maybe you're right,' he admitted, and I don't think he had often used those words in his lifetime. 'But it still makes no difference. You want me to help you, but I can't. You'll never beat him -and if you did I'd still be wanted for murder. I'd rather stick to Ramirez and take my chances. He still needs me.'

I wanted to try and tell him how wrong he was, but something else had finally penetrated to my consciousness. There was a whistling sound in the distance – high pressure steam was escaping somewhere. Mark looked out of the porthole and what he saw over the water made him acutely unhappy. 'Damn them, what are they doing on deck?' he muttered. 'This is no time to be hanging around here.'

His nervousness increased and he conferred with one of the guards in a low voice. An argument seemed to develop as the guard answered back, but Mark overbore him. With a black glance and a reluctant shrug the guard opened the saloon door and went out.

I looked at Geordie with hopeful eyes and he nodded grimly. The odds were improving, but anything we tried would have to be done before the guard returned. Geordie's hand crept towards the heavy glass ash tray on the table and then relaxed near it. He couldn't throw it faster than the guard could shoot – but he was ready if a chance came up. We were all sitting tensely.

There was a reddish reflection in Mark's face as he went again to look out of the porthole. Evidently things were stirring on Falcon. I said, 'What's going on out there, Mark?'

His voice was strained. 'It looks as though Falcon is going to bust loose.'

I felt suddenly colder. Mark and I were possibly the only two people on either ship qualified to have any understanding of what that might mean. I said, 'How close are we?'

'Maybe a quarter of a mile.' He straightened his back and added, 'It's happened a couple of times this week already. It's never amounted to much. A great sight, but that's all.' But he was not convincing.

We were much too close to Fonua Fo'ou. To Ramirez and Hadley it might seem a good safe distance, especially if they had been watching pre-eruption patterns all week, but Mark and I knew better. We knew what volcanic eruptions could do.

No wonder Mark was scared. So was I.

He looked at the remaining guard, hesitated, and then spoke to him. The guard shook his head vigorously, and as Mark started to leave he stepped in front of the door and raised his rifle.

Campbell said ironically, 'What's the matter, Mark? Doesn't he trust you?'

The whistling and belching suddenly increased and Esmerelda lurched, her joints squealing a protest. We swung round, still locked with Sirena. There was a sudden blast of an acrid sulphurous smell in the air. Mark's eyes darted from the guard to me and our glances locked as tightly as the ships.

Mark said sharply, 'He doesn't want to be left here alone with you lot. I must wait for the other guard.' He crossed to the porthole and looked out again and I felt bile rise in my throat.

Geordie said, 'What the hell's the matter…?'

He didn't have time to finish. Esmerelda gave another great lurch and went over almost on her beam ends. I slithered helplessly towards the side of the saloon and jarred my head against the table as I fell. There were sounds of bedlam above decks.

The ship righted herself and we fell back in a jumble of bodies. I heard Campbell groan; it must have been hell for him in his condition. Geordie was up first. He grasped the ashtray and hurled it at the guard, and then leapt the length of the saloon. The guard tried frantically to retrieve his rifle from the deck where it had fallen. He had his fingers on the butt when Geordie kicked him with precision in the jaw and his face disappeared into a bloody ruin.

Ian had gone for Mark and any trace of his normal Highland gentleness had vanished. His face was a mask of rage. Geordie had grabbed the rifle and turned it on Mark. They converged on him, but Mark managed to evade them both and scrambled towards the saloon door.