Geordie was routed.

Campbell broke in impatiently at this point. 'What about the diary, Mike? You've read through it, I suppose.'

'There are interesting possibilities opening up.'

'How come?'

'The diary was written partly while Mark was with the IGY survey. Now, he made a record of those high-cobalt nodules, but the fact never came out in the open scientific record. In other words, he suppressed the evidence.'

Campbell seemed perturbed. 'I shouldn't think your brother would do a thing like that,' he said stiffly. And that told me that any reservations he may have about Mark stemmed from Mark's personal affiliation with Clare, and that he had never plumbed the depths of Mark's personality. I would have to be careful, but it was time to bring things out into the open.

I said, 'Can you think of any other explanation?'

He shook his head. 'I'm at a loss what to make of it – I have been giving it some thought already. Are you serious when you said your brother would do a thing like that? He struck me as a very fine scientist.'

'Mark was never too scrupulous,' I said. 'He wanted something from you and he was showing his cleanest face.'

Campbell didn't like that. My open distrust of Mark offended his sense of fitness. Brothers should be brotherly and blood is thicker than water. I suspected he had a strong puritan streak in him, inherited from his no doubt calvinistic ancestors. He said, almost hostilely, 'There's nothing to be gained by running down your brother – especially as he can't answerback.'

I said softly, 'You should study the Bible, Mr Campbell.

There are a few stories in the Book that are very illuminating. Read about Cain and Abel, or Esau and Jacob. There's no hard and fast rule that brothers should like one another – and lots of villains have innocent kinfolk.'

He was acid. 'Well, I suppose you knew him best. I never had any reason to doubt him while he was in my employ.' He caught Clare's eye and faltered just a little. 'Must admit that personally…'

Clare's face was calm, showing only a polite interest, but her jawline caught my notice.

I said, 'We must discuss this. We're faced with a problem put to us by Mark and we can only solve it by understanding him and the way he worked. Geordie can support some of what I may have to tell you.' I had them all riveted now. 'Let me tell you something that I'll bet you don't know – Mark was kicked out of the IGY for falsifying figures. That was just before he joined your company.'

'I didn't know that and I don't think I believe it.'

'It's true,' I said. 'Professor Jarvis, my old boss at the Institute, told me about it – and Geordie heard him too. I think he got hold of those nodules at the time, found out their value, and decided to keep the knowledge to himself. Then he moved in on you – and he was using you.'

Campbell was affronted. 'Using me!' 'You had the money he wanted for an expedition. He couldn't show you the nodules because you'd want to know where he got them. And that was by stealing them from the people who paid his salary.'

Campbell began to look baffled. 'He never showed me anything. He talked a good story though.'

That's right. He had a lot of theory and you nearly fell for it. If you had, he'd have wasted his time and your money fossicking round the Pacific for six months and then his "theory" would have led him to a spectacular find. You see, he knew where those nodules came from. Anyway you'd be in the chips and he'd be both rich and vindicated – the great scientist.'

Campbell nodded unwillingly.

I said, 'But something went wrong. You had your run-in with Suarez-Navarro and found yourself strapped for ready funds. You couldn't finance his expedition, and so he left you flat because you were of no further use to him. Isn't that so?'

There was silence while Campbell digested all that.

'All right, you've made your point – don't drive it into the ground. Assuming something like that is possible – what do you suggest we do now?'

'First, another point. You wondered how Suarez-Navarro came into the nodule hunt. I think Mark may have tried the same ploy on them. In fact I think he and Norgaard were waiting in Tahiti for the ship that's being fitted out right now, and that ties everything in squarely together.'

'All right, let's assume that too. We're safer the more we can see into the forest, I suppose.' Campbell was still shaken by what I'd said about Mark. 'What do we do next?'

'Well, we could find out where Mark's IGY ship dredged and drop ours in the same places. But I don't think it will be any of the sites they actually surveyed or this would have come out already – Mark wasn't the only one doing assays. No, I think it was a trial site, one they weren't serious about, and probably didn't even make a record of, though we could check it out.'

We all sat in gloom for a while. The faint drift of music changed tempo and a woman began to sing with the trio, and I turned to watch her. Her voice was nice but she was no world-beater. Her body was better than her voice and set off admirably by a revealing gown. For a moment, lost in something not at all of our troubled world, I relaxed and only caught the end of a sentence directed at me by Clare Campbell.

'… to ask you a question – if I'm not distracting you, Mike?' Her voice was calm but when I turned back I saw an ironic sparkle in her eyes.

'Sorry, yes?' I said.

'You say that Mark was kicked off the ship for falsifying figures – but which figures? Not the high-cobalt nodule assay because, as you said, that news hasn't broken yet. So he must have falsified other figures which caught him out. What were they and why did he cook them – could they matter?'

That was something I hadn't thought of, and it was a stopper. I said, 'Mark was always a fast boy with a red herring. He cheated once in his school exams, and this is how he did it. He was called into the headmaster's office just before an exam and the master happened to be out of the room. On the desk was a pile of question papers. Mark played it cleverly – he didn't take one, he took six. Then he made a copy for himself and passed the six papers to other boys -anonymously.'

Campbell said, 'I don't get it.'

'It's simple. He told me about it afterwards – he always knew I wouldn't tell tales. He reckoned that if the thing blew up in his face he'd see to it that the six papers were all found -in the possession of other boys. He'd be in the clear. It wasn't found out and he got away with it. Now what if he's done something like that here?'

Campbell looked frustrated. He was supposed to be a man with acumen, after all. 'I may be dumb, but I still don't get it.'

'Look,' I said patiently. 'Mark has located a deposit of high-cobalt nodules and he's busy suppressing the information. He knows that if he's found out he's not only in disgrace but he's lost a potential fortune. So – knowing Mark – I'd guess that he'd toss out a few red herrings. He'd falsify some more figures to confuse the issue, and he'd probably revise all estimates upwards. It would add slightly to the risk of discovery, but if it was found out, as it evidently was, he'd be only another glory-hunting scientist, rather too optimistic and looking for professional praise. No one would suspect that one set of figures was wrong for another reason. They may not ever have caught it.' I laughed humourlessly. 'I'll bet that all Mark's findings were junked, anyway. None of his colleagues would trust his figures after that.'

'Why didn't they tell the world about it – to protect people like Pop?' asked Clare a little bitterly.

'I think they would feel that commercial folk like your dad can take care of themselves,' I said. 'They're mostly too gentlemanly.'

Campbell was looking at me in wonder, Geordie in silent assent of my assessment. 'Did Mark really have a mind like that?' Campbell said.