Gambler Nathan Detroit has few options for the location of his big craps game. Needing $1,000 to pay a garage owner to host the game, Nathan bets Sky Masterson that Sky cannot get virtuous Sarah Brown out on a date. Despite some resistance, Sky negotiates a date with her in exchange for bringing people into her mission. Meanwhile, Nathan's longtime fiancée, Adelaide, wants him to go legit and marry her.

Danforth is assigned to take over the police department in a section of a large city saddled with juvenile delinquency, petty crimes, graft and also a recent unsolved murder of a strip-tease dancer. Recognizing the laxity of the department he implements many changes and soon finds himself under fire by the newspapers, the attorney of a racket leader and the denizens of this human jungle.