- Emily Brent: Very stupid to kill the only servant in the house. Now we don't even know where to find the marmalade.
- Philip Lombard: Hello puss, looking for a mouse? So are we.
- Judge Francis J. Quinncannon: What I'd like to know is if we're the cat, or the mouse.
- Thomas Rogers: You think I poisoned those cocktails! Well, I'll show you, sir! Picking on an innocent man! I can't touch even a drop of alcohol - and if that's what you think of me, I'm not going to serve any dinner!
- Detective William Henry Blore: One thing is for certain; he ain't inside so he must be outside.
- Philip Lombard: Brilliant thinking, Blore.
- Dr. Edward G. Armstrong: We all build islands of imagination. Represents escape. Half of my patients are sick because they're trying to escape reality.
- Judge Francis J. Quinncannon: Well, and what's your answer?
- Dr. Edward G. Armstrong: Oh, I tell them fairytales. I build them islands of imagined security.
- Judge Francis J. Quinncannon: Don't you believe in medicine, Doctor?
- Dr. Edward G. Armstrong: Do you believe in justice, Judge?
- Judge Francis J. Quinncannon: We tell the story in Ireland about the two Englishmen who were cast away on a desert island for three years and never spoke to each other, because they hadn't been introduced.
- Detective William Henry Blore: I know who took the dining room key!
- Philip Lombard: Who?
- Detective William Henry Blore: Rogers! He had the key to the dining room, fact. He unlocks the door, takes a little Indian, goes out and chops up some sticks, fact. And then...
- Philip Lombard: And then he takes the chopper, and splits his own cranium, fact. I'd like to see you do that to yourself, Blore. It would take practice!
- Judge Francis J. Quincannon: So you see, the whole thing has been as inevitable as in a nursery rhyme. When the boat arrives from the mainland, there will be ten dead bodies, and a riddle no one can solve on Indian Island.
- Dr. Edward G. Armstrong: Maybe we've been wrong, built up a nightmare out of imagination.
- Judge Francis J. Quinncannon: Two people dead isn't imagination.
- Judge Francis J. Quinncannon: Mr. Owen could only come to the island in one way. It's perfectly clear. Mr. Owen is one of us.
- [last lines]
- Fred Narracott: Good morning. Ready to leave now?
- Philip Lombard: Ha, are we.
- Fred Narracott: Are the others ready too?
- Philip Lombard: You call them.
- [Narracott enters the house while Lombard and Claythorne run off together]
- [Prince Nikita Starloff has just collapsed after taking a drink]
- Philip Lombard: He's not moviing.
- Detective William Henry Blore: Just plain drunk.
- Dr. Edward G. Armstrong: Just plain dead.
- Philip Lombard: Mr. Owen's hand is plain to see.
- Judge Francis J. Quinncannon: Yes, but where the devil is Mr. Owen himself?
- Vera Claythorne: I'm afraid it's no use watching for the boat. It won't come until Monday.
- General Sir John Mandrake: [staring out to sea] No boat will ever come, Juliet. We're here forever. What made you love him, Juliet?
- Judge Francis J. Quincannon: Don't forget the old proverb, Doctor. Never trust a man who doesn't drink.
- Detective William Henry Blore: Sounds like the Bible. Great book.
- Thomas Rogers: May I ask you a question?
- Detective William Henry Blore: Of course, of course my dear fellow.
- Thomas Rogers: How many will you be for dinner tonight?
- Detective William Henry Blore: But... Oh! I see what you mean.
- Thomas Rogers: [Pours a drink into a glass. Hiccups.]
- Judge Francis J. Quinncannon: [Reaches for the glass.] Don't put any water in.
- Thomas Rogers: I shan't, sir.
- [Sits down in an armchair, lounges in it, and drinks from the glass.]
- Thomas Rogers: They're saying it's me because I'm only a butler. You said I didn't have the brains to do it.
- Dr. Edward G. Armstrong: I didn't vote for you, Rogers.
- Thomas Rogers: Well, who did then?
- Dr. Edward G. Armstrong: Who didn't drink the cocktail you just served?