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.
| Directing | Robert Rossen | Director |
| Writing | Robert Rossen | Screenplay |
| Camera | Burnett Guffey | Director of Photography |
| Production | Jerry Giesler | Producer |
| Art | Bill Black | Props |
| Art | Newsboy Brown | Props |
| Writing | Milton Holmes | Original Story |
| Editing | Al Clark | Editor |
| Production | Edward G. Nealis | Producer |
| Sound | Morris Stoloff | Music Director |
| Art | James Crowe | Set Decoration |
| Directing | Carl Hiecke | Assistant Director |
| Art | Stephen Goosson | Art Direction |
| Crew | John P. Barrett | Technical Advisor |
| Sound | Jack Haynes | Sound Recordist |
| Editing | Warren Low | Editor |
| Costume & Make-Up | Jean Louis | Costume Design |
| Crew | Joe Palma | Stunts |
| Camera | Ned Scott | Still Photographer |
| Sound | George Duning | Original Music Composer |
| Crew | Wally Rose | Stunts |
| Art | Cary Odell | Art Direction |
| Sound | Arthur Morton | Orchestrator |
| Production | George Lait | Publicist |
| Production | Milton Holmes | Associate Producer |
| Crew | Leo Schlesinger | Stunts |
