ça parle d'un double meurtre dans rue .
si tu doit parler du livre je peut te mettre de trois truc si tu veut :)
"You will say that I was puzzled; but, if you think so, you must have misunderstood the nature of the inductions. To use a sporting phrase, I had not been once `at fault.' The scent had never for an instant been lost. There was no flaw in any link in the chain. I had traced the secret to its ultimate result, -- and that result was the nail. […] `There must be something wrong,' I said, `about the nail.' I touched it; and the head, with about a quarter of an inch of the shank, came off in my fingers. The rest of the shank was in the gimlet-hole, where it had been broken off. (page 72)
We have here a small-scale example of the logic Dupin uses when he thinks "Ourang-Outang" and then interviews the sailor for evidence. Dupin has examined all of the other possible ways of entering and exiting the death room and found them to be impossible. Thus, he is certain that the killer(s) came in via the window. So he looks carefully at the nail to find that there is a broken nail. There's scientific method in this: Dupin presents a hypothesis and then goes out and gets proof.