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 tête."
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.
"That's all I know about the murder," he said at last, "but there are plenty of complications apart from that. I suppose Miss Byrne told you that my uncle electrified us all by saying she was his daughter, only an hour or so before he died?"