'Ah. So everyone knows about that?' Doone seemed disappointed.

'John just told us,' Tremayne nodded.

Doone gave me a sorrowful stare, but I hadn't given a thought to his wanting secrecy.

'They didn't float, sir, because they were weighted.'

'With what?' Sam asked.

'With pieces of paving stone. There are similar pieces of paving stone scattered on a portion of your boatyard property.'

'Paving stone?' Sam sounded bemused, then said doubtfully, 'Do you mean broken slabs of pink and grey marble?'

'Is that what it is, sir, marble?' Doone didn't know much about marble, it appeared.

'It might be.'

Doone pondered, made up his mind, went out to his car and returned carrying a five-foot plank which he laid across the kitchen table. The old grey wood, though still dampish, looked as adequate for its purpose as its fellows still forming the boathouse floor and didn't seem to have been weakened in any way. Slightly towards one end, on the surface that was now uppermost on the table, rested a long, unevenly shaped darkish slab of what I might have thought was rough-faced granite.

'Yes,' Sam said, glancing at it. 'That's marble.' He stretched out his hand and tried to pick it up, and the plank came up an inch with it. Sam let it drop, frowning.

'It's stuck on,' Doone said, nodding. 'From the looks of the other pieces lying about, the surface that's stuck to the wood is smooth and polished.'

'Yes,' Sam said.

'Superglue, we think,' Doone said, 'would make a strong enough bond.'

'A lot of plastic adhesives would,' Sam said, nodding.

'And how do you happen to have chunks of marble lying about?' Doone asked, though not forbiddingly.

'It came with a job-lot of stuff I bought from a demolition firm,' Sam explained without stress. 'They had some panelling I wanted for a boat I did up, and some antique bathroom fittings. I had to take a lot of oddments as well, like the marble. It came from a mansion they were pulling down. They sell off things, you know. Fireplaces, doors, anything.'

Doone asked conversationally, 'Did you stick the marble on to the floorboards, sir?'

'No, I sodding well did not,' Sam said explosively.

'On to the underside of the floorboards,' I said.

'There were no slabs of marble in sight when Harry and I went into the upstairs room of the boathouse. I expect, if there are some other blocks still in place, that you can see them from underneath, in the dock.'

Doone with slight reluctance admitted that there seemed to be marble stuck to the underside of one more floorboard on each side of the hole.

The plank on the table was about eight inches across. Harry had taken three of them down with him; five altogether had been doctored. The trap with its missing section of beam had been three and a half feet across, and Harry, taking the envelope bait, had gone through its centre.

'Have you finished snooping round my place now?' Sam demanded, and Doone shook his head.

'I want to work on my boat,' Sam objected.

'Go ahead, sir. Never mind my men, if they're there.'

'Right.' Sam stood up with bouncing energy, quite unlike a patient suddenly stricken with flu. 'Bye, Tremayne. Bye, Mackie. See you, John.'

He went out to his car carrying his jazzy jacket and tooted as he drove away. The kitchen seemed a lot less alive without him.

'I'd like to talk to Mr Kendall alone,' Doone said placidly.

Tremayne's eyebrows rose but he made no objection. He suggested I took Doone into the dining-room while he told Mackie about Roydale's gallop, and Doone followed me docilely, bringing the plank.

The formality of the dining-room furnishings seemed at first to change his mood from ease to starch, but it appeared to me after a short while that he was troubled rather by indecision as to which side I was now on, them or us.

He seemed to settle finally for us, us being the police, or at least the fact-seekers and, clearing his throat, he told me that his men with grappling irons and magnets had missed finding the floorboards the first time, probably because the floorboards weren't magnetic. Did I, he wanted to know, think the trap-setter had taken magnetism into account.

I frowned. 'Stretching it a bit,' I said. 'I should think he looked around for something heavy that would take glue, and with all that junk lying around there was bound to be something. The marble happened to be perfect. But the whole thing was so thoroughly thought out, you really can't tell.'

'Do you know who did it?' he asked forthrightly.

'No,' I said truthfully.

'You must have opinions.' He shifted on his chair, looking around him. 'I'd like to hear them.'

'They're negative more than positive.'

'Often just as valuable.'

'I'd a.s.sume the trap-setter had been a guest at Sam Yaeger's boatyard party,' I said, 'only you warned me never to a.s.sume.'

'a.s.sume it,' he said, almost smiling and in some inner way contented.

'And,' I went on, 'I'd a.s.sume it was the person who killed Angela Brickell who wanted to fix the blame for ever on Harry by making him disappear, only-'

'a.s.sume it,' he said.

'Anyone could have killed Angela Brickell, but only a hundred and fifty or so people went to Sam's party, and half of those were women.'

'Don't you think a woman could have set that trap?' he asked neutrally.

'Sure, a woman could have thought it out and done the carpentering. But what woman could have lured Angela Brickell and persuaded her to take all her clothes off in the middle of a wood?'

He sucked his teeth.

'All right,' he said, 'I agree, a man killed her.' He paused, 'Motive?'

'I'd guess- to keep a secret. I mean, suppose she was pregnant. Suppose she went out into the woods with- him, and they were going to make love- or they'd done it- and she said "I'm pregnant, you're the father, what are you going to do about it?" She was full of jumbled religious guilts but it was she who was the seducer-' I paused. 'I'd think perhaps she was killed because she wanted too much- and because she wouldn't have an abortion.'

He made a sound very like a purr in his throat.

'All right,' he said again. 'Method: strangulation. Guaranteed to work, as everyone around here knew, after the death of that other girl, Olympia.'