discuss locked room mysteries and now we have one of our own?'
'Two,' said Diamond, and now he began to function more constructively. 'There's the mystery of the stamp and the mystery of the murder. It may be that Keith is right, and the stamp theft was a tactical move in a more serious game. We'd better keep an open mind. Since the stamp came up first, let's confine ourselves to that for a moment. Milo Motion can't explain how the Penny Black got between the pages of his book, which incidentally was The Hollow Man, by John Dickson Carr-if that means anything at all to a crowd of bozos who never read anything except the Sun. He kept it on a shelf on his boat with his other books. He had no visitors during the past week. On the evening of the meeting, he removed the book from the shelf and took it to the Bloodhounds. It didn't leave his possession at all. He's very clear about that. So what are we left with? The stamp was already between the pages when he took The Hollow Man from the bookshelf. John and I have seen the boat. It isn't very long. About sixty-five feet. Motion says he bolts it from the inside whenever he's aboard and padlocks it from the outside when he isn't. If the thief planted the stamp, he found a way to beat the locks and bolts. The cabin area of that boat is a perfect locked room. No hatches. No way in by the windows, which just have a narrow vent at the top. There's a door at either end. One end is bolted from the inside. Chubb security bolts at top and bottom. We've seen them. The other is locked from outside with this strong, close shackle padlock, and there's only one key-on a ring in Motion's pocket.'
Keith Halliwell suggested, 'Could the thief have unscrewed the fittings on the door?'
'The padbar and staple, you mean?' said Diamond. 'Nice try. We looked at it ourselves. The screws are rusty, so any recent interference would show. There isn't a scratch.'
'The hinges?' someone else put in.
'They aren't accessible from7 outside-and they haven't been tampered with.'
Halliwell said, 'Someone must have a duplicate key, whatever Mr. Motion says.'
'We've checked with the locksmith. It isn't possible. It's a feature of these locks, which are German-made, that each one is unique. There were two keys, but he dropped his spare one in the canal over a year ago. I simply don't believe that some passing bandit could have fished it out and knew which padlock it fitted.'
Halliwell was a stubborn cuss. 'If he put his keys down somewhere, someone could have done the old Plasticine trick and got an impression.'
'If,' said Diamond. 'But he insists that they are always in the pocket of the trousers he is wearing.'
'There's the flaw. Can we believe him?'
'I'd say yes.'
'There's got to be some explanation.'
'You might be interested in what Dickson Carr had to say on the subject.' Diamond felt into his jacket pocket and with a flourish produced a paperback of The Hollow Man. 'Chapter seventeen is 'The Locked-Room Lecture,' the one Milo Motion planned to read to the Bloodhounds. The author states among other things that the explanation of a locked room problem is invariably disappointing.'
' 'So simple when it is explained,'' murmured Wigfull.
'What?'
'A quote from a Sherlock Holmes story.'
'This is John Dickson Carr,' Diamond said brusquely. 'I was going on to say that in this lecture he classifies most of the methods used in locked room mysteries. I won't bore you with them all. He dismisses secret panels, secret passages, and so on as trick stuff, beneath contempt. He's pretty scathing about murders that are committed without the murderer actually entering the room, by gases, mechanical devices, and so on. And about suicide, when the gun disappears up the chimney on the end of a piece of elastic.'
The gun on elastic earned some chuckles.
'As a variation it can be whisked out of a window. Then there are bullets made of ice that melt without a trace. There are poisonous snakes, impersonations, disguises, tricks with time. But the section of most interest to us is the one on ways of tampering with door locks. As Dickson Carr sums it up, there are three categories. First, the murderer can use bits of string and metal to turn a key which is still in a lock, but on the wrong side of the door. This doesn't apply to our problem. Secondly, he can remove the door hinges, as someone suggested, but in our case it didn't happen. Thirdly, he tampers with the bolt, using string or metal. One of our sets of doors, you'll recollect, was bolted from inside. However, the bolts aren't the primitive things Dickson Carr was describing in 1935. They're finger-bolts, set into the wood, invisible from the outside, and I defy anyone to open them with string, plastic, or anything else. If the killer isn't Milo Motion-and it can't be, for reasons I've stated-then he or she must have found a way of unfastening the padlock.'
'Which is impossible,' said Wigfull. 'This is a sophisticated padlock with only one key, which remained in Mr. Motion's possession throughout the time I was questioning him.'
'Are you certain it was locked when you arrived at the boat with Mr. Motion?' Julie Hargreaves asked.
Wigfull nodded. 'I watched him closely. I had my torchbeam pointed at the lock. I saw him take the key from his pocket and use it. There was a click as he turned the key, and the shackle of the padlock sprang open. I haven't the slightest doubt that I saw the padlock being unlocked.'
'Do we have a time for the murder?' Fred Baker, one of Diamond's more senior detectives, asked.
'You know what pathologists are like about times of death,' said Diamond. 'All he would say-if I can call the phrase to mind-was that the external symptoms were not inconsistent with a time of death up to four hours prior to when he examined the body. We know the poor sod was alive four hours before.'
'And what was the cause?'
'Give me a break, Fred. We haven't had the postmortem yet. It was pretty obvious that he'd received a heavy blow on the head, but if I tell you he died of brain damage you can be damned sure the postmortem will show he choked on a fishbone.'
After a short pause, Keith Halliwell asked, 'What do we know about the victim? Was there any bad blood between him and Motion?'
'Apparently not. Motion claims they were on cordial terms. He says Towers was an introvert, excessively shy. Hardly ever joined in the discussions at the Bloodhounds. Wouldn't even look you in the eye unless he was forced to. He worked as a night watchman in a furniture warehouse. Monday was his night off.'
'Any family?'
'No. He lived alone in a top-floor flat in Oak Street, off the Lower Bristol Road, under the railway viaduct.'
'Did he drive?'
'Good point. How did he get to the boatyard? He owned an old Skoda. And before anyone asks, yes, it was one of the cars parked near the entrance. We can safely assume that Sid Towers drove there after the Bloodhounds' meeting broke up. On the passenger seat we found a plastic bag containing a secondhand copy of-you guessed-a John Dickson Carr novel.'
'The Hollow Man?'
'No. The Three Coffins. I haven't read it yet.'
'You'll be lucky to get the time, sir,' Baker was bold enough to comment.
'I will, if you lot get your fingers out. The first thing is to find out about what happened last night at the Bloodhounds. Apart from Motion and the victim, there were five others in attendance: four women and one man. I'll give you the names presently. I want them interviewed this morning before the news of the murder breaks. If you're assigned to one of them, play it cautiously. You're on the case of the Penny Black as far as they're concerned. They know they witnessed something bloody unusual. They'll be expecting you, so get them to talk about the moment when Motion opened his book and found the stamp. Try and get a picture of what else happened at the meeting- whether anything was said by the victim or anyone else that could have provoked violence later. See if Sid Towers confided in anyone before he drove to the boatyard. I'm damned sure this murder has its origin in the Bloodhounds, so I want to know what drives these people, their hang-ups, their ambitions, the tensions between them, what they eat for breakfast, and what keeps them awake at night.' He turned to Wigfull. 'John, have I left anything out?'
Wigfull cleared his throat. 'I don't want anyone forgetting that we're also investigating the stamp theft,' he said huffily. 'This is more than just a pretext for getting the facts about the murder. It's a serious crime that may or may not be connected with what happened to Towers. Be alert. Insist that you get a full account of the events leading up to the discovery of the Penny Black cover, and what happened after.'
'Got that? The Penny Black is Mr. Wigfull's baby, and the murder is mine. And if one of you messes up, you
