Убийства по алфавиту

"Vous prouvez trop d'emotion, Hastings. It affects your hands and your wits. Is that a way to fold a coat? And regard what you have done to my pyjamas. If the hairwash breaks what will befall them?"
"Good heavens, Poirot," I cried, "this is a matter of life and death. What does it matter what happens to our clothes?"
"You have no sense of proportion, Hastings. We cannot catch a train earlier than the time that it leaves, and to ruin one's clothes will not be the least helpful in preventing a murder."

But if you are a sufficiently great and important person, it is necessary that you should be spared small annoyances. If a fly settles on your forehead again and again, maddening you by its tickling — what do you do? You endeavour to kill that fly. You have no qualms about it. You are important — the fly is not. You kill the fly and the annoyance ceases. Your action appears to you sane and justifiable. Another reason for killing a fly is if you have a strong passion for hygiene. The fly is a potential source of danger to the community — the fly must go. So works the mind of the mentally deranged criminal.

If I had 'simply asked,' as you put it, I should have got no answer at all to my questions. You yourself are English and yet you do not seem to appreciate the quality of the English reaction to a direct question. It is invariably one of suspicion and the natural result is reticence. If I had asked those people for information they would have shut up like oysters.
But by making a statement (and a somewhat out-of-the-way and preposterous one) and by your contradiction of it, tongues are immediately loosened.

"Your same old joke. One of the beautiful girls, of course, must be unjustly suspected — and there's some misunderstanding between her and the young man. And then, of course, there must be some other suspects — an older woman, dangerous type — and some friend or rival of the dead man's — and a quiet secretary — dark horse — and a hearty man with a bluff manner — and a couple of discharged servants or gamekeepers or something — and a damn fool of a detective rather like Japp — and well — that's about all."
...
Poirot looked at me sadly. "You have made there a very pretty résumé of nearly all the detective stories that have ever been written."