“Two months ago,” he said, “as you may possibly remember, a man called James Rolls was hanged at Beltonborough for the most atrocious murder of his wife. The deed apparently was quite objectless; there had been no quarrel, and after it was done he seemed sometimes to be distressed at the crime, sobbing and crying, sometimes to gloat over it, recounting it with gusto. There was no question whatever about his guilt, only about his sanity, and with regard to that these fits of remorse and enjoyment might be assumed in order to produce the impression that he was not accountable for his actions. He was examined by a Government expert, who asked me to come down with him and form my conclusion. We could neither of us find any other symptom of insanity about him. But there was a certain conjecture in my head about what we call the history of the case, and I stopped down at Beltonborough for a day or two in order to make further observations. “As I was having an interview with him, I suddenly asked him this question, ‘Did you begin by killing flies?’ Usually he was rather sullen and silent, and often would not answer; but when I asked him this, his eye brightened, and he said, ‘Yes, flies first, and then cats and dogs.’ After that I could get nothing further out of him, but I had got what I expected to get. In all other respects he was, as far as I could judge, perfectly sane, and it was scarcely possible to call him a homicidal maniac, for he had never before shown signs of wanting to take human life. As it was, he had committed an atrocious murder, and had he been shut up as a homicidal maniac, I do not think there is any doubt that by this time he would have killed a warder. “Now no man in a fit of rage is altogether sane, and yet we do not commute the sentence of those who have killed another when beside themselves with passion, and James Rolls had not even that extenuation. He was hanged.... But I feel convinced that Frank is suffering from an early stage of James Rolls’s malady; I feel convinced also that the hanging of James Rolls infected him with it.” “The hanging of James Rolls caused it?” I asked. “I do not doubt it, as you will see when I state my theory. But I hope to prove that my theory is correct, and I hope to cure my cousin.” Roupert sat up and looked at me while he said this; then he sank back in his chair again, and, as before, covered his eyes with his hands.