An ex-tennis pro carries out a plot to murder his wife. When things go wrong, he improvises a brilliant plan B.

Tony Wendice: It's funny to think that just a year ago, I sat in that Knightsbridge Pub actually planning to murder her. And I might have done it, if I hadn't seen something that changed my mind.
C.A. Swan: Well? What did you see?
Tony Wendice: I saw you.
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!
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: At exactly three minutes to eleven, you'll enter the house through the street door. You'll find the key to this door under the stair carpet here.
C.A. Swan: The fifth step?
Tony Wendice: That's the one. Go straight to the window, and hide behind the curtains. At exactly eleven o'clock, I shall go to the telephone in the hotel to call my boss. I shall dial the wrong number. This number. That's all I shall do.
Tony Wendice: [to Mark] People don't commit murder on credit.
Margot Mary Wendice: Anyone would have realized he was dead. Just one look at those staring eyes...
Chief Insp. Hubbard: So you did see his face, after all.
Margot Mary Wendice: I saw his eyes! I can't remember his face!
C.A. Swan: [referring to the bribe money Tony is offering him to kill Margot] You know the police would only have to trace one of these notes back to you to hang us both from the same rope?
Tony Wendice: They won't. For a whole year I've been cashing an extra twenty pounds a week, always in fivers. I then change them for those at my leisure.
C.A. Swan: Let me see your bank statement.
Tony Wendice: By all means. Don't touch.
[Tony opens up his checkbook for Swan, so as not to leave fingerprints]
C.A. Swan: [as he reads] Turn back a page.
[Tony complies]
C.A. Swan: Ah, your balance has dropped by over a thousand pounds during the year. Suppose the police ask you about that?
Tony Wendice: I go dog-racing twice a week.
C.A. Swan: They'll check your bookmaker!
Tony Wendice: Like you, I always bet on the "Tote." Satisfied?
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.
Mark Halliday: What is all this?
Chief Insp. Hubbard: They talk about flat-footed policemen. May the saints protect us from the gifted amateur.
Margot Mary Wendice: How long have you known this?
Chief Insp. Hubbard: Did you suspect it yourself?
Margot Mary Wendice: No, never. And yet... What's the matter with me, Mark? I don't seem able to feel anything.
[last lines]
Tony Wendice: As you said Mark, it might work out on paper, but congratulations, Inspector. Oh, by the way... How about you, Margot?
Margot Mary Wendice: Yes, I could do with something.
Tony Wendice: Mark?
Mark Halliday: So could I.
Tony Wendice: I suppose you're still on duty, Inspector.
Mark Halliday: [to Margot] Darling, I understand now, but that doesn't stop me from loving you.
[first lines]
Margot Mary Wendice: let me get you another drink. Mark, before Tony comes I ought to explain something.
Mark Halliday: Yes, I've been waiting for that.
Margot Mary Wendice: I haven't told him anything about us.
Chief Insp. Hubbard: [to Mark and Margot] Mind you, even I didn't guess that at once... extraordinary.
C.A. Swan: Well that's the first and last reunion I ever went to. What a murderous thug I look.
Tony Wendice: Yes, you do, rather.
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.
Mark Halliday: How long have you known about Tony, Inspector?
Chief Insp. Hubbard: Well... to be perfectly honest, the very first clue came quite by accident.
[to Margot]
Chief Insp. Hubbard: We discovered that your husband had been spending large sums of pound banknotes all over the place and it seemed to have started around the time that you were arrested. My orginal investigation was to find out where Mr. Wendice was getting all this money and how. After several months of investigating and reaching nothing but dead ends from visits to his bank to loan companies and to investigating crimminal robberies, I remembered something. On the day that you were arrested when I first visisted here, I remembered catching a glipse of his bank statement in the desk by the window. So yesterday afternoon, I went to the prison and asked to see your handbag. While I was doing this, I managed to lift your latchkey. Highly irregular, of course, but my blood was up. And this morning while your husband was out I came back here to let myself in to see his bank statement. I never saw it... because I never got through that door. You see, the key that I took out of your handbag didn't fit the lock.
Margot Mary Wendice: Oh, there you are. We thought you were never coming. What have you been up to?
Tony Wendice: I'm sorry darling, but the boss came in just as I was leaving.
Margot Mary Wendice: Tony, this is Mark Halliday.
Tony Wendice: Hello Mark.
Mark Halliday: Hello.
Chief Insp. Hubbard: So yesterday afternoon, I went to the prison and asked to see your handbag. While I was doing this, I managed to lift your latchkey. Highly irregular, of course, but my blood was up.
C.A. Swan: You know, I think I must have seen you somewhere since we left Cambridge.
Tony Wendice: Ever been to Wimbledon?
C.A. Swan: That's it! Wendice. Tony Wendice. What's all this about "Fisher"?
Tony Wendice: What's all this about "Lesgate"?
[embarrassed, Swan doesn't respond]
Tony Wendice: Would you like a cigar?
C.A. Swan: Smart, aren't you?
Tony Wendice: No, not really. I've just had time to think things out. Put myself in your position. That's why I know you're going to agree.
C.A. Swan: What makes you think I'll agree?
Tony Wendice: For the same reason that a donkey with a stick behind him and a carrot in front always goes forwards and not backwards.
C.A. Swan: Tell me about the carrot.
Margot Mary Wendice: Don't make me stay home. You know how I hate doing nothing.
Tony Wendice: Doing nothing? Why there are hundreds of things you can do. Have you written to Peggy, thanking her for the weekend? And what about those clippings? It's an ideal opportunity.
Margot Mary Wendice: Well I like that. You two go gallivanting while I stay home and do those boring clippings.
C.A. Swan: Where's the nearest police station?
Tony Wendice: Opposite the church, two minutes walk.
C.A. Swan: Suppose I walk there now.
Tony Wendice: What would you tell them?
C.A. Swan: Everything.
Tony Wendice: Everything? All about "Mr. Adams" and "Mr. Wilson"?
C.A. Swan: I should simply tell them that you're trying to blackmail me into...
Tony Wendice: ...Into?
C.A. Swan: ...murdering your wife.
Tony Wendice: [chuckles] I almost wish you would. When she heard that we'd have the biggest laugh of our lives.
C.A. Swan: Aren't you forgetting something?
Tony Wendice: Am I?
C.A. Swan: You've told me quite a lot tonight.
Tony Wendice: What of it?
C.A. Swan: Suppose I tell them how you followed her to that studio in Chelsea and watched them cooking spaghetti and all that rubbish. Wouldn't that ring a bell?
Tony Wendice: Oh, it certainly would. They'd assume you followed her there yourself.
C.A. Swan: Me? Why should I?
Tony Wendice: Why should you steal her handbag? Why should you write her all those blackmail notes? Can you prove you didn't? You certainly can't prove I did. It'll be a straight case of your word against mine.
C.A. Swan: That'd puzzle them, wouldn't it? What could you say?
Tony Wendice: I should simply say that you came here tonight, half-drunk, and tried to borrow money on the strength that we were at college together. When I refused, you mentioned something about a letter belonging to my wife. As far as I could make out, you were trying to sell it to me. I gave you what money I had, and you gave me the letter. It has your fingerprints on it, remember? Then you said if I went to the police you'd tell some crazy story about my wanting you to murder my wife. Before you go any further, old boy, do consider the inconvenience. You see, I'm quite well known, and there'd be pictures of you as well. And sooner or later there'd be a deputation of landladies and lodgers who would step forward and testify as to your character. And someone is almost certain to have seen you with Miss Wallace. You were careful not to be seen around with her, I noticed. You usually met in out-of-the-way places where you wouldn't be recognized.
Tony Wendice: Would any of you fellows have the right time?
Men's Club party member: Yes, I have. It's seven minutes past eleven.
Mark Halliday: I make it only just after that.
Tony Wendice: My watch has stopped. I must have over wound it.
Men's Club party member: So, as I was saying...
Tony Wendice: Excuse me, old boy, I have to call my boss.
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?
Chief Insp. Hubbard: There is evidence however that he was blackmailing you.
Tony Wendice: Blackmail?
Mark Halliday: Yes, I'm afraid it's true, Tony.
Chief Insp. Hubbard: And you suggest that he came in by the window. And we know that he came in by that door.
Margot Mary Wendice: But he can't have come in that way. That door was locked. And there are only two keys. My husband had his with him, and mine was in my handbag. Here.
Chief Insp. Hubbard: You could have let him in.
Chief Insp. Hubbard: Good morning, Sir. I'm Chief Inspector Hubbard, in charge of criminal investigation of this division.
Tony Wendice: Oh, I think we gave your sergeant all the necessary information.
Chief Insp. Hubbard: Yes, I've seen his report of course, but there are a few things I'd like to get firsthand.
Tony Wendice: [on the phone] I don't see why we can't settle this whole thing here and now, provided you drop the price.
C.A. Swan: [on the phone] I'm afraid that's quite out of the question.
Tony Wendice: [on the phone] Well, we'll see what a couple of drinks can do. Goodbye.
C.A. Swan: [on the phone] Goodbye.
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.
C.A. Swan: When would this take place?
Tony Wendice: Tomorrow night.
C.A. Swan: Tomorrow? Not a chance! I've got to think this over.
Tony Wendice: It has to be tomorrow. I've arranged things that way.
C.A. Swan: Where?
Tony Wendice: Approximately where you're standing now.
Tony Wendice: How about coming with me to a stag party?
Mark Halliday: A stag party?
Tony Wendice: Yes, some American boys have been playing tennis all over the country. We're giving them a sort of farewell dinner.
Mark Halliday: Sounds great, but I'm not much of a tennis player.
Tony Wendice: Doesn't matter. You know New York and all that.
[to Margot]
Tony Wendice: Darling, Mark's coming to the party tomorrow night.
Margot Mary Wendice: Oh good. You better drop in here first and have a drink.
Tony Wendice: That's the idea.
Mark Halliday: Yes, alright. Well I'll try and get a taxi.
Margot Mary Wendice: No, we can usually pick one up. So long, darling.
Tony Wendice: Enjoy yourself.
Mark Halliday: So long, Tony.
Tony Wendice: Good night.
Chief Insp. Hubbard: Sooner or later, he'll come back here. As I've pinched his latch key, he'll try the one in the handbag. When that doesn't fit, he'll realize his mistake, put two and two together, and look under the stair carpet.
Mark Halliday: If he doesn't do that, all of this is pure guess work. We can't prove a thing.
Chief Insp. Hubbard: That's perfectly true. But once he opens that door, we shall know everything.
Margot Mary Wendice: Why did you bring me here?
Chief Insp. Hubbard: Because you were the only other person who could possibly have left that key outside. I had to find out if you knew it was there.
Margot Mary Wendice: Suppose I had known?
Chief Insp. Hubbard: You didn't.
Tony Wendice: One thousand pounds in cash.
C.A. Swan: For a murder?
Tony Wendice: For a few minutes work, that's all it is. And no risk, I guarantee. That ought to appeal to you. You've been skating on pretty thin ice.
C.A. Swan: I don't know what you're talking about.
Tony Wendice: You ought to know. It's in all the papers. Middle aged woman found dead due to an overdose of something. Apparently, she'd been taking the stuff for quite some time, and nobody knows where she got it. But we know, don't we? Poor Miss Wallace.
C.A. Swan: This thousand pounds. Where is it?
Tony Wendice: It's in a small attaché case in a check room.
C.A. Swan: Where?
Tony Wendice: Somewhere in London. Of course we don't meet again. As soon as you've delivered the goods, I shall mail you the checkroom ticket and the key to the case. You take this hundred pounds on account.