Johnny Clay (Sterling Hayden) is a veteran criminal planning one last heist before settling down and marrying Fay (Coleen Gray). He plans to steal $2 million from the money-counting room of a racetrack during a featured race. He assembles a team consisting of a corrupt cop (Ted de Corsia), a betting window teller (Elisha Cook Jr.) to gain access to the backroom, a sharpshooter (Timothy Carey) to shoot the favorite horse during the race to distract the crowd, a wrestler (Kola Kwariani) to provide another distraction by provoking a fight at the track bar, and a track bartender (Joe Sawyer).
George Peatty, the teller, tells his wife Sherry (Marie Windsor) about the impending robbery. Sherry is bitter at George for not delivering on the promises of wealth he once made her, so George hopes telling her about the robbery will placate and impress her. Sherry does not believe him at first but, after learning that the robbery is real, enlists her lover Val Cannon (Vince Edwards) to steal the money from George and his associates.
The heist is successful, although the sharpshooter is shot and killed by a security guard after he runs over a horseshoe that had been offered to him for good luck but was thrown to the ground and has a flat tire on his car. The conspirators gather at the apartment where they are to meet Johnny and divide the money. Before Johnny arrives, Val appears with an associate and holds them up. A shootout ensues and a badly wounded George emerges as the only man standing. He goes home and shoots Sherry before collapsing.
Johnny, on his way to the apartment, sees George staggering in the street and knows that something is wrong. He buys the biggest suitcase he can find to put the money in (and struggles to lock it properly). At the airport Johnny and Fay are not allowed to take the case on their flight due to its size. Instead, they must check it as regular luggage. Johnny reluctantly complies. While waiting to board the plane the couple watch the suitcase fall off a baggage cart onto the runway after a dog runs out on the runway and the baggage cart driver swerves to avoid it, break open, and the loose banknotes scattered and then swept away by the backdraft from the aircraft’s propellers.
Fay and Johnny try to leave the airport immediately, but they are unable to hail a cab before officers are alerted to them. Fay urges Johnny to flee; however, he refuses, calmly accepting the futility of trying to escape, and utters the final line, “What’s the difference?”. The film ends with two officers approaching to arrest him.