Down on his luck, Cruz Ross tries to win all the money he needs at an underground card room to save his family. After winning more than enough, he's faced with the dilemma to go big or just go home.
When an employee at an illegal gambling den dies suspiciously, her sister, Nancy, looks into the situation and falls for Johnny O'Clock, a suave partner in the underground casino. Selfish and non-committal by nature, Johnny slowly begins to return Nancy's affection and decides to run away with her, but conflict within his business threatens their plans. As Johnny tries to distance himself from the casino, his shady past comes back to haunt him.
Childhood chums Rocky Sullivan and Jerry Connelly grow up on opposite sides of the fence: Rocky matures into a prominent gangster, while Jerry becomes a priest, tending to the needs of his old tenement neighborhood.
A psychotic man opens fire in a diner, murdering numerous people before killing himself. The survivors struggle in different ways following this horrendous event: a doctor doubts his own instincts and elects to use an experimental medical procedure on his wife, while a gambler believes he's on a lucky streak. A waitress begins engaging in promiscuous sex, and a young girl whose father is among the dead gains unexpected fame.
A naive young man assumes a dead man's identity and finds himself embroiled in an underground world of power, violence, and chance where men gamble behind closed doors on the lives of other men.
Ulrich Mott is an eccentric and versatile social climber with grandiose plans to affect United States foreign policy. Encouraged in his attempts by his strategically chosen (and much older) wife, the well-connected journalist Elsa Brecht, Mott has a knack for making himself indispensable and impossible to ignore. The only one seemingly immune to his charms is Elsa's daughter Amanda, who might simply disapprove of her mother marrying a much younger man - or perhaps she senses something more sinister beneath the smooth-talking surface?