When San Francisco bookmaker Hal Towers confides in his boss, racketeer Dan Gannin, that a syndicate is trying to force him to pay protection money, Dan reminds him about their recent pledge to get out of the gambling racket. Although Dan offers his best friend a chance to invest in his new, legitimate nightclub, Hal insists on fighting the syndicate. Dan cautions Hal, who is lame, to be careful, but before the night is over, Dan and another childhood friend, police detective Barney Runson, find the bookie lying dead at the bottom of his apartment stairs. Concerned for his friend's safety, Barney warns Dan not to seek vengeance on Hal's killers, but allow the law to pursue justice. Dan's associates, however, expect him to retaliate for Hal's murder, and Dan obeys the rules of gangster protocol by not revealing anything about the case to Barney. When Dan goes home that night, he is greeted by two well-dressed men who present themselves as "insurance salesmen." Anxious to discover who is behind the syndicate, Dan agrees to consider their protection offer, but the next day, the men see Barney at Dan's office and, assuming he is talking to the police, leave in a huff. Once again, Dan refuses Barney's request for information, and later criticizes his girl friend, Robbie Lawrence, for nagging him about being careful. After dropping Robbie home that night, Dan is accosted by two thugs, who blindfold him and take him to see their boss. Without revealing his identity, the boss gives Dan another chance to join the syndicate, but Dan refuses. Unaware that Robbie is sitting in the room with the boss, Dan is then beaten up by the thugs. After Barney has Dan released from the hospital, he questions Robbie at her apartment and comments that her face looks familiar to him. Dan then advises his bookmakers not to fight the syndicate, but allow him to take care of the problem. The next day, Dan's sister Elaine, a singer at his nightclub, begs Dan to stop his crusade, but he insists on finding Hal's killer. Unable to convince Dan to cooperate with him, Barney takes him to an old vaudeville theater and shows him a photograph of Robbie, a former showgirl, with husband Phil Dixon, the syndicate boss. Although Robbie, who told Dan she was a war widow, insists that she hasn't seen Dixon in years, Dan knows she is lying as he had smelled her perfume in Dixon's office the previous night. When confronted with the truth, Robbie confesses her deception but insists that Dixon forced her to betray him. Then, pledging her love to Dan, she agrees to leave San Francisco with him that night. As Dan is leaving Robbie's apartment, however, he overhears the desk clerk relaying a telephone call from her to Dixon and eavesdrops on the conversation. Now sure of Robbie's double-cross, Dan returns home, where he is put under protective custody by Barney. As Barney and Dan are leaving, Al, one of Dan's bookies, stops them at gunpoint and declares his allegiance to the syndicate. Dixon then arrives and is about to take Dan and Barney away when Dan instigates a fight. During the mêlée, Dan intercepts a bullet meant for Barney, who then knocks out Dixon. After Barney acknowledges his friend's sacrifice, Dan dies in his arms.