Bloodhounds

is that we found it and confirmed what you heard about the paint marks. Pretty damning. This writing on the gallery window was a desperate attempt by Rupert to throw suspicion on someone else, wouldn't you say?'

'Looks that way,' Diamond said.

'And when it didn't succeed, when you followed up yesterday, asking for him in all his usual haunts, he heard we were onto him and topped himself.'

Diamond wasn't having that. He hadn't hounded Rupert to his death. 'You're wrong there, John. This hanging wasn't something he thought of yesterday evening. It couldn't have been.'

This drew a frown from Wigfull.

Patiently and without condescension, Diamond explained. 'It was in the third riddle:

'To end the suspense, as yours truly did,

Discover the way to Sydney from Sid.' '

Wigfull's long, silent look showed that he dearly wanted to know what Diamond was getting at.

'The riddle predicted this hanging,' Diamond went on.' 'To end the suspense': That's what happened this morning. Rupert was suspended from the bridge. When he was cut down, we ended the suspense. It was a play on words, John, a gruesome double meaning. So it was all planned. 'Discover the way to Sydney' is what we did, except that we guessed wrong and picked the bloody museum instead of the bridge. If we'd thought more about every sodding word in the riddle, we might have anticipated this.'

'Might not.'

Really, Diamond had to agree. The lines had tantalized, as the previous riddles had. To have penetrated their true meaning would have required the brilliance of one of those fictional sleuths the Bloodhounds revered. He knew his limitations.

Wigfull took a more positive line. 'At least you have your murderer, and I have my locked room thief,' he pointed out. 'All we have to do now is work out how it was done.'

'You're assuming Rupert Darby is your man?'

'Aren't you?' said Wigfull, blushing scarlet.

Diamond said, 'If you really want to know, John, I think you couldn't be more wrong. I know how it was done, but I'm damned if I know who did it.'

'You're talking about the locked room mystery? You think you've cracked it?' said Wigfull on a shrill note of disbelief.

Diamond had cracked it all right. He was certain now, after thinking it through, going over it many times in his mind since getting the flash of inspiration the evening before. As he'd told Julie at the time, the breakthrough had come with her question: 'What was the murderer doing there?'

Between them, on a table, labeled and bagged, were the contents of the dead man's pockets. Diamond pointed to the polythene bag containing the padlock. 'Take a look. Is it, or is it not, indistinguishable from the padlock on the narrowboat?'

Wigfull turned it over several times. 'It's the same make, certainly. But we've been through this before, my theory about a substitute padlock. You know we have. I thought I had the answer until you showed it was impossible. This padlock can't have been used. Milo's was on the door when we opened it that night, and he had only the one key. You proved that yourself when your divers found his old bunch of keys in the canal and the damned thing fitted. This doesn't prove anything unless the keys happen to be identical, and we were told by the locksmith that such a thing couldn't happen.'

'Just in case, let's put that to the test,' said Diamond. He went to a drawer and took out Milo's padlock and the key that fitted it. 'Pass me the other bag, would you-the one containing Rupert's keys?'

'Do you think you ought to be handling them?' said Wigfull.

'The keys, please.'

Wigfull shook the bag and dropped the key ring on the table top. He wasn't going to risk leaving his prints on them.

All work was suspended in the incident room. Everyone in there-detectives, filing clerks, computer operators-gathered around the two senior men. Julie Hargreaves was there, and Keith Halliwell, on tenterhooks to hear the explanation.

There were four keys on the ring: one of the Yale type that looked like a front-door key; a plastic-topped one that was probably for a car; and two small narrow ones, identical in shape. Diamond slotted one of the latter into Milo's padlock and tried unsuccessfully to turn it. To leave no one in any doubt, he tried the other, still with no result.

Wigfull said smugly, 'You see. It doesn't match. Let's compare it with Milo's key. I'm willing to bet the whole shape is different.'

He was right. When placed together, the two keys were clearly cut for different locks.

Diamond was not discouraged. Far from it. 'Right. This is the way it was done. It's going to make you groan, it's so simple. This is Milo's padlock, right? And this is the key that fits it, the one key available at the time. Milo had possession of the key, so Milo was the only person who could open the padlock at any time. Everyone agreed?'

There were some cautious murmurs. Nobody really wanted to be shown up as gullible.

'Now imagine Milo going to his locked boat anytime you like. He uses his key to open the padlock. Now what does he do?'

Halliwell said, 'Removes the key and replaces it in his pocket.'

Diamond wagged a stubby finger in confirmation. 'Right. The keys go back into his pocket. What about the padlock?'

'He doesn't put that in his pocket,' said one of the computer operators. 'It's too bulky.'

'So what does he do?'

'Leaves it hanging on the staple.'

'Correct. Locked or unlocked?'

A moment's hesitation. Then, from Wigfull: 'Unlocked, presumably. No point in locking it while he's at home. If he wants privacy, he can use the fingerbolts on the inside of the door.'

Diamond gave a nod and referred the matter to everyone else by spreading his hands. 'Reasonable? Now, let's take this on a bit. Milo is aboard his boat, sitting in the cabin watching TV or cooking. The door is bolted from the inside. The padlock is hanging from the staple outside the door with the shackle-this arched bit at the top- unfastened. Anyone could lift the padlock off. Are you with me still?'

There were nods and murmurs all around.

'Now along comes our villain with a similar padlock- different key, of course-unhooks Milo's padlock and substitutes his own. Done in a moment without Milo being aware of it. He goes away and waits for his opportunity.'

There were definite sounds of understanding.

'You're onto it, aren't you?' said Diamond. 'Milo decides to go out. And what does he do to lock his door? Simply closes it, lifts off the padlock-the new padlock, believing it to be his own-and slots the hasp over the staple. Puts the padlock in position and presses it home. He doesn't need to use his key. They lock automatically, as anyone who has used a padlock knows.'

They were not only up with his explanation now; they were ahead. The murmurs were of appreciation.

'But of course,' Diamond said, 'the padlock he's just attached to his boat belongs to the villain, who can now unlock it at will. So the villain lets himself in, does his dirty work, and leaves. And when he leaves, he fixes Milo's padlock on the door and presses it closed. Milo comes back later, unlocks as usual, and can't fathom how someone could have got inside his cabin.'

Julie said, 'Nor could anyone else until this moment.'

Halliwell said, 'You've cracked it.'

Even Wigfull was nodding.

A couple of people applauded, and almost everyone joined in.

Diamond flushed with embarrassment and reminded them that there was work to be done. His stock had never been higher at the Bath nick.

Later, at the bridge in Sydney Gardens, he examined the scene of the hanging. The approaches were still cordoned off. The Scenes of Crime officers had come and gone. Part of the rope was still attached to the iron parapet.