"I hope so," said Gimblet, but his voice was full of doubt. "It's hard to see how anyone else could have used his rifle after he cleaned it, since he admits that he locked it up and kept the key on him. Yes," he murmured to himself, "the rifle speaks very eloquently. What other interpretation can be put on these facts? I'm sure you must see that yourself," he went on, glancing up at Mark, who was feeling in his pocket for another cigarette. "Sir David told Miss Byrne he had cleaned his rifle; he told the police he then locked it up and that the key had been in his possession ever since. But the rifle was found to have been fired again since he had cleaned it. His only explanation was to contradict what he had previously said to Miss Byrne. Do those facts appear to you to leave any possible loophole of doubt as to his guilt?" Mark struck a match and lighted his cigarette before he answered. When at length he did so his reluctance was very plain, and his voice full of regret. "Poor old chap," he said. "I'm afraid he must have done it in some fit of madness. As you say, there is no other imaginable alternative." Gimblet nodded philosophically. "Is there anything else?" he asked. Mark hesitated. "There's a letter which arrived for Uncle Douglas this morning," he said, "which you may think worth looking at. I daresay it's of no importance, but it struck me as rather odd." He took a letter out of his pocket and handed it to the detective, who opened it and read as follows: "Si Milord ne rend pas ce qu'il ne doit pas garder, le coup de foudre lui tombera sur la tete." There was no signature, nor any date. Gimblet turned the sheet over thoughtfully. The message was typewritten on a piece of thin foreign paper; the postmark on the envelope was Paris, and the stamps French. He folded it again and replaced it in its cover. "It seems the usual threatening anonymous communication," he observed. "Have you any idea who it's from?" Mark shook his head. "None," he confessed. "It looks, though, as if my uncle had in his possession something belonging to the writer, doesn't it? Don't you think it might have something to do with the murder?" "I don't see why the murderer should send a threatening letter after the deed was done," said the detective. "Still less could he have posted it in Paris on the very day the crime was committed." "No, that's true enough," Mark admitted reluctantly. "Has any suspicious looking person been seen about this place, this summer? Any foreigner, for instance?" asked the detective. "No; no," Mark replied. "I should have heard of it for certain if there had been. It would have been an event, down here." Gimblet dropped the subject. "If I may," he said. "I will keep this. It may lead to something," he added, tucking the letter away in an inside pocket. "That's all, I suppose?" Mark was silent for a minute. He seemed to be thinking.