Japp nodded. ‘I don’t say you’re not right. But all the same, you won’t get a jury to take much note of a jailbird’s evidence. What seems odd to me is that Lowen couldn’t find a cleverer way of disposing of the ring.’

Poirot shrugged his shoulders. ‘Well, after all, if it were found in the neighbourhood, it might be argued that Davenheim himself had dropped it.’

‘But why remove it from the body at all?’ I cried.

‘There might be a reason for that,’ said Japp. ‘Do you know that just beyond the lake, a little gate leads out on to the hill, and not three minutes’ walk brings you to—what do you think?—a lime kiln.’

‘Good heavens!’ I cried. ‘You mean that the lime which destroyed the body would be powerless to affect the metal of the ring?’

‘Exactly.’

‘It seems to me,’ I said, ‘that that explains everything. What a horrible crime!’

By common consent we both turned and looked at Poirot. He seemed lost in reflection, his brow knitted, as though with some supreme mental effort. I felt at last his keen intellect was asserting itself. What would his first words be? We were not long left in doubt. With a sigh, the tension of his attitude relaxed and turning to Japp, he asked:

‘Have you any idea, my friend, whether Mr and Mrs Davenheim occupied the same bedroom?’

The question seemed so ludicrously inappropriate that for a moment we both stared in silence. Then Japp burst into a laugh. ‘Good Lord, Monsieur Poirot, I thought you were coming out with something startling. As to your question, I’m sure I don’t know.’

‘You could find out?’ asked Poirot with curious persistence.

‘Oh, certainly—if you really want to know.’

‘Merci, mon ami. I should be obliged if you would make a point of it.’ Japp stared at him a few minutes longer, but Poirot seemed to have forgotten us both. The detective shook his head sadly at me, and murmuring, ‘Poor old fellow! War’s been too much for him!’ gently withdrew from the room.

As Poirot seemed sunk in a daydream, I took a sheet of paper, and amused myself by scribbling notes upon it. My friend’s voice aroused me. He had come out of his reverie, and was looking brisk and alert.

‘Que faites-vous là, mon ami?’

‘I was jotting down what occurred to me as the main points of interest in this affair.’

‘You become methodical—at last!’ said Poirot approvingly.

I concealed my pleasure. ‘Shall I read them to you?’

‘By all means.’

I cleared my throat.

‘“One: All the evidence points to Lowen having been the man who forced the safe.

‘“Two: He had a grudge against Davenheim.

‘“Three: He lied in his first statement that he had never left the study.

‘“Four: If you accept Billy Kellett’s story as true, Lowen is unmistakably implicated.”’