New York City, 1950. Mark Dixon is a city police detective who is demoted by Inspector Foley due to his frequent use of violence, a trait rooted in his own father’s criminal past. In a hotel elsewhere in town, gangster Tommy Scalise hosts a floating crap game that ends with the death of a visiting Texas tycoon. Police are summoned, including Dixon, who had once arrested Scalise for murder but was later acquitted.
During the investigation, detectives learn that newspaper columnist Ken Paine and a model, Morgan Taylor, had left the game early. Dixon joins the inquiry and visits Paine at his apartment. In questioning, Paine’s drunken belligerence becomes too much for Dixon; in self-defense, he slugs Paine, killing him. It soon emerges that Paine wore a metal plate in his head as a result of a war injury.
Fresh from his demotion for violence, Dixon tries to conceal what happened. He borrows Paine’s coat and puts a bandage on his own face where Paine had one, laying a false trail that Paine left town. Back at Paine’s apartment, Dixon narrowly avoids being seen by Morgan Taylor’s father, cab driver Jiggs Taylor, who bursts in, learns Paine slapped his daughter, and threatens Paine from outside before leaving when there’s no answer. Dixon then transports Paine’s corpse to the river, where it’s dumped, but the body is soon discovered. To cover his tracks, Dixon suggests Scalise murdered Paine as well as the Texas tycoon.
As the case unfolds, detectives question Morgan and Jiggs Taylor. It’s revealed that Morgan was Paine’s estranged wife, and the night of the Scalise gathering was the first time she had seen him in months. Dixon still insists Scalise is the killer, but Jiggs is arrested after being seen at Paine’s apartment. A complicated romance grows between Dixon and Morgan, yet he cannot bear to tell her the truth. He arranges a top lawyer for Jiggs—one who has never lost a murder case—but the attorney refuses the case.
After a tense confrontation with Scalise, Dixon writes a letter addressed to Inspector Foley, marked “to be opened in the event of my death.” He plans to meet Scalise again, believing that at least this time accountability will follow. Scalise anticipates this and shoots Dixon in the arm rather than killing him. Then one of Scalise’s men arrives with news that police have learned the truth about the tycoon’s murder from an informant. As the gang attempts to escape via a car elevator, Dixon stalls it until the police arrive. Back at the precinct, Foley—proud of Dixon’s work—returns the letter unopened, but Dixon asks him to read it. Foley arrests Dixon, and Morgan witnesses, still believing in him. When she asks why he’s being taken into custody, Dixon asks Foley to show her the letter; even knowing the truth, her love remains undaunted, and she declares that he will not be punished for the accidental death.
