Frank McCloud travels to a run-down hotel on Key Largo to honor the memory of a friend who died bravely in his unit during WW II. His friend's widow, Nora Temple, and wheelchair bound father, James Temple manage the hotel and receive him warmly, but the three of them soon find themselves virtual prisoners when the hotel is taken over by a mob of gangsters led by Johnny Rocco who hole up there to await the passing of a hurricane. Mr. Temple strongly reviles Rocco but due to his infirmities can only confront him verbally. Having become disillusioned by the violence of war, Frank is reluctant to act, but Rocco's demeaning treatment of his alcoholic moll, Gaye Dawn, and his complicity in the deaths of some innocent Seminole Indians and a deputy sheriff start to motivate McCloud to overcome his Hamlet-like inaction.

The gangster Colorado kidnaps Marshal McKenna. He believes that McKenna has seen a map which leads to a rich vein of gold in the mountains and forces him to show him the way. But they're not the only ones who're after the gold; soon they meet a group of "honorable" citizens and the cavalry crosses their way too - and that is even before they enter Indian territory.

Tony Manetta runs an unsuccessful Miami hotel, on which he can't meet the payments. Another liability is his weakness for dames (Shirl, his sexy current flame, is even less responsible than Tony). But a solid asset is Ally, his sensible 12-year-old son. When Tony wants stolid brother Mario to bail him out again, Mario makes conditions: give up Ally, or at least get married to a "nice, quiet little woman" of his selection. Tony and Ally just play along to be diplomatic, but when the woman in question proves to look like Eleanor Parker...

In 1930s New Orleans, the Cincinnati Kid, a young stud poker player who travels from one big game to the next, stopping along the way up with various girls, is pitted against the legendary champion card-sharp Lancey Howard in a high-stakes poker game.

Former bootlegger Remy Marco has a slight problem with forclosing bankers, a prospective son-in-law, and four hard-to-explain corpses.

In 1938, Walter Neff, an experienced salesman of the Pacific All Risk Insurance Co., meets the seductive wife of one of his clients, Phyllis Dietrichson, and they have an affair. Phyllis proposes to kill her husband to receive the proceeds of an accident insurance policy and Walter devises a scheme to receive twice the amount based on a double indemnity clause. When Mr. Dietrichson is found dead on a train-track, the police accept the determination of accidental death. However, the insurance analyst and Walter's best friend Barton Keyes does not buy the story and suspects that Phyllis has murdered her husband with the help of another man.