‘But I repeat,’ Alleyn went on, ‘that it is circumstance, opportunity and behaviour that must concern us. Opportunity, after a fashion, you all had. Miss Ralston and Mr Leiss were on the premises late that night. They had stolen the cigarette-case and the case was found by the body. The trap was laid by somebody wearing leather and string gloves and Mr Leiss had lost such a pair of gloves.’

Leonard and Moppett began to talk together but Alleyn held up his hand and they stopped dead.

‘Their behaviour, however, doesn’t make sense. If they were planning to murder Mr Cartell they would hardly have publicized their actions by singing and whistling under Mr Period’s window.’

Moppett gave a strangulated sob, presumably of relief.

‘Lady Bantling had opportunity and she knew the lie of the land. She could have set the trap but it’s obvious she didn’t do so as she was seen by Mr Bantling and Miss Maitland-Mayne, returning, across the planks, to her car. She, too, had publicized her visit by serenading Mr Cartell from the garden. Her behaviour does not commend itself as that of an obsessive, maternal murderess.’

‘Too kind of you to say so,’ Desirée murmured.

‘Moreover, I fancy she is very well aware that her son could anticipate his inheritance by borrowing upon his expectations and insuring his life as security for the loan. This reduces her motive to one of mere exasperation and the same may be said of Mr Bantling himself.’

‘And of me,’ said Bimbo quickly.

Alleyn said: ‘In your case there might well be something we haven’t yet winkled out. Which is what I mean about the secondary importance of motive. However, I was coming to you. You had ample opportunity. You retired to a bathroom where you tell me you spent a long time bandaging your hand. You could equally well have spent it driving back to the ditch and arranging the trap. No, please don’t interrupt. I know you were bitten. That proves nothing. You may also remember that you took Mr Leiss’s overcoat to him. Were his gloves in the pocket?’

‘How the hell do I know! I didn’t pick his ghastly pockets,’ said Bimbo, turning very white.

‘A statement that at the moment can’t be checked. All the same, there’s this to be said for you: if you are both telling the truth about your movements this evening, you are unlikely to have chucked the paper-weight at Mr Period’s head. Although,’ Alleyn said very coolly, ‘the amorous dog-chase might well have led you into Mr Period’s garden.’

‘It might have,’ Desirée remarked, ‘but in point of fact it didn’t. Bimbo was never out of my sight.’

‘If that is so,’ Alleyn said, ‘it leads us to an inescapable conclusion.’