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