‘How do you know?’ Alleyn asked. ‘She might have cut up rough on some other provocation. She had her evidence. The possession of a dangerous instrument is, in itself, a danger. Even if you had never visited the Island, Miss Emily, Barrimore and Maine would still have laughed at the Festival.’

‘She would have been less disturbed by their laughter,’ said Miss Emily. She looked fixedly at Alleyn. ‘I am tiring you, no doubt,’ she said. ‘I must go. Those kind children are waiting in the motor. I merely called to say au revoir, my dear Roderique.’

‘You are not tiring me in the least and your escort can wait. I imagine they are very happy to do so. It’s no good, Miss Emily. I know you’re eaten up with curiosity.’

‘Not curiosity. A natural dislike of unexplained detail.’

‘I couldn’t sympathize more. Which details?’

‘No doubt you are always asked when you first began to suspect the criminal. When did you first begin to suspect Dr Maine?’

‘When you told me that, at about twenty to eight, you saw nobody but Wally on the road down to Fisherman’s Bay.’

‘And I should have seen Dr Maine?’

‘You should have seen him pulling out from the bay jetty in his launch. And then Trehern, quite readily, said he saw the doctor leaving in his launch about five past eight. Why should he lie about the time he left? And what, as Trehern pointed out, did he do in the half-hour that elapsed?’

‘Did you not believe that poor woman when she accounted for the half-hour?’

‘Not for a second. If he had been with her she would have said so when I first interviewed her. He has a patient in the hotel and she could have quite easily given that as a reason and would have wanted to provide him with an alibi. Did you notice his look of astonishment when she cut in? Did you notice how she stopped him before he could say anything? No, I didn’t believe her and I think he knew I didn’t.’

‘And that, you consider, was why he ran away?’

‘Partly that, perhaps. He may have felt,’ Alleyn said, ‘quite suddenly, that he couldn’t take it. He may have had his moment of truth. Imagine it, Miss Emily. The blinding realization that must come to a killer: the thing that forces so many of them to give themselves up or to bolt or to commit suicide. Suppose we had believed her and they had gone away together. For the rest of his life he would have been tied to the woman he loved by the most appalling obligation it’s possible to imagine.’

‘Yes,’ she said. ‘He was a proud man, I think. You are right. Pray go on.’