One night, while trying to arrest racketeer boss Delinko, hard-bitten police sergeant Steve Keenan is forced to kill the gangster in self-defense. At the squad room the next day, after officer Duncan accuses Steve of having a vendetta against Delinko because the racketeer was living with Steve's one-time girl friend Laura Wallace, Steve vehemently denies the charge; however, Delinko is the second man Steve has killed who dated Laura. Steve's brother Harry, who is also a police officer, assures him that everyone is glad Delinko is dead and congratulates him on yet another success in his police career. Harry, however, cautions Steve to be careful and shows him a note found at the Delinko apartment warning Steve that "No matter what the laws calls it, I call it murder." Steve is unconcerned by the threat and visits Lucky's Club to apologize to his girl friend Gerri, a singer at the bar, for standing her up the previous evening. Meanwhile, Laura has Delinko's chauffeur Mouse drive her to a jewelry store near Lucky's. Recognizing Delinko's car, Steve interrogates Mouse about the name of the note's author, but Mouse claims no one in the crime syndicate cared enough about Delinko's death to write the note. When Laura returns to the suite of the new racketeer boss, Chessner, he accuses her of planning to meet Steve and reminds her that she chose racketeering money over the sergeant's good looks. He then reminds her that since Delinko is dead, he has inherited everything, including her. Later, when Laura comes to the police bail out Chessner's gunman Junior, she tells Steve that she never stopped loving him and, as she walks out the door, Junior sees Laura and Steve together. That night, at the apartment that Steve shares with Harry, Harry's girl friend Sandy calls Steve a "headline hungry" cop, but Steve accuses her of secretly liking him more than Harry and forces her to kiss him. Later, after Harry shows Steve another threatening note warning "You're a dead man," Steve asks bar owner Lucky to use his underworld contacts to identify who might want to kill him. Meanwhile, Harry, concerned that Sandy prefers Steve, questions her about why she is waiting to accept his marriage proposal, adding that Steve has already stolen one of his girl friends. Late that night, Sandy goes to Harry's apartment and finds Harry lying beaten on the floor. When Sandy calls Steve at Lucky's, Gerri picks up the phone, and, hearing Sandy's voice, assumes Steve is having another affair. Steve believes that someone mistook Harry for him and suspects Chessner of the crime, but when Steve confronts Chessner at his apartment that night, Chessner reiterates that no one regrets Delinko's death. Once outside, Steve finds Junior is following him and knocks him out, later learning that Junior was killed just minutes after Steve hit him. Back at Lucky's, Gerri laments that waiting for Steve is pointless, since he will never recognize her love for him. Lucky concurs and warns her that Steve will break her heart. Meanwhile, as the police look for Steve in connection with Junior's death, Chessner has sent Duke to kill Steve to avenge Junior. Harry sends Sandy to Lucky's to warn Steve that both the police and the gangster are after him. Steve then learns from Lucky that Delinko's brother is in town and is possibly seeking revenge. Realizing Laura may have information useful to him, Steve calls Chessner's and asks to see her. While Laura is on the phone, Chessner orders her to lure Steve to his apartment. Driving Sandy's car, Steve arrives at the apartment and using Georgie, Chessner's lackey and elevator boy, as a shield, at bursts into the apartment at gunpoint, throwing Georgie into Chessner's gunfire. Escaping unharmed, Steve returns to Lucky's, where a tearful Laura calls to tell him Chessner is coming to kill him. Moments later, Duncan and Mouse come to the club looking for Steve. Steve disarms Mouse and forces him to take him and Sandy to Delinko's brother's hotel room, where the brother, seated at a table, tells Steve that Delinko's death was not unexpected. When the man does not respond to Steve's bullying or his accusations about writing the threatening notes, Steve turns over the table to find that Delinko's brother is handicapped and wears leg braces. Realizing his mistake, Steve leaves with Sandy for her apartment, where Sandy insists he stay even though this puts her own life in peril. Thinking about the series of incidents, Steve questions why the man behind the threats did not kill Harry, instead of beating him up, when he mistook him for Steve. Finally realizing that threats are a convenient cover-up, Steve is about to tell Sandy that it is Harry who seeks to kill him, when his brother walks in with his gun pointed at Steve. As a demented Harry explains that he has no identity of his own because Steve has stolen the limelight since they were young, Steve moves away from Sandy, allowing her to pull out a gun she has hidden in her purse while Steve grabs Harry's gun. Harry lurches at Steve with a letter opener, challenging Steve to kill him and asking if he is callous enough to kill his own brother. In his struggle, Harry falls back into Sandy's gun, which fires and kills him. Sandy weeps and accuses Steve of never showing Harry nor anyone else any love. Later at the police station, Steve learns that Chessner was arrested for Georgie's death and that Laura is looking for him. Ready to begin a new life, Steve ignores Laura's call and meets Gerri. After admitting that they do not know each other well, Steve proposes to her and Gerri tells him that her love for him is all that she needs to know.