Mark Halliday: [to Margot] Darling, I understand now, but that doesn't stop me from loving you.

Mark Halliday: What is all this?
Chief Insp. Hubbard: They talk about flat-footed policemen. May the saints protect us from the gifted amateur.

Tony Wendice: [on the phone to a lawyer] Carl, it's me. We have a problem here. Our flat was broken into last night and Margot was attacked. No... she's all right. The man was killed. The police are here now, and don't laugh... but they're suggesting that Margot killed him intentionally.
Chief Insp. Hubbard: [interupting Tony] I wouldn't say that if I were you, sir.

Tony Wendice: [on the phone with Margot] I'm so glad we don't have to go to Maureen's; she's such a filthy cook.

Tony Wendice: [to C.A. Swan] By the way does Mrs. Van Dorn know about Mr. Adams or Mr. Wilson and Miss Wallace? You were planning to marry Mrs. Van Dorn, weren't you?

Tony Wendice: [to Mark] People don't commit murder on credit.

Tony Wendice: How do you go about writing a detective story?
Mark Halliday: Well, you forget detection and concentrate on crime. Crime's the thing. And then you imagine you're going to steal something or murder somebody.
Tony Wendice: Oh, is that how you do it? It's interesting.
Mark Halliday: Yes, I usually put myself in the criminal's shoes and then I keep asking myself, uh, what do I do next?
Margot Mary Wendice: Do you really believe in the perfect murder?
Mark Halliday: Mmm, yes, absolutely. On paper, that is. And I think I could, uh, plan one better than most people; but I doubt if I could carry it out.
Tony Wendice: Oh? Why not?
Mark Halliday: Well, because in stories things usually turn out the way the author wants them to; and in real life they don't... always.
Tony Wendice: Hmm.
Mark Halliday: No, I'm afraid my murders would be something like my bridge: I'd make some stupid mistake and never realize it until I found everybody was looking at me.

Tony Wendice: What makes you think he came in by this door?
Chief Insp. Hubbard: His shoes.
Tony Wendice: His shoes?
Chief Insp. Hubbard: The ground was soaking wet last night. If he'd come in by the garden, he'd have left mud all over the carpet. As it is, he didn't leave any marks at all, because he wiped his shoes on the front doormat.
Tony Wendice: How can you tell?
Chief Insp. Hubbard: It's a fairly new mat, and some of its fibers came off on his shoes.
Tony Wendice: Oh, but surely...
Chief Insp. Hubbard: And there was a small tar stain on the mat, and some of the fibers show that as well. There is no question about it.

Chief Insp. Hubbard: [Detective Pearson is about to leave with Mrs. Wendice's small purse around his wrist] Oh, wait a minute, you clot; you can't walk down the street like that - you, you'll be arrested!

Chief Insp. Hubbard: [to Mark and Margot] Mind you, even I didn't guess that at once... extraordinary.