Gambler and fight promoter Jim Lambert, grants Gunner O'Brien his dying wish and agrees to care for Gunner's granddaughter, Mona, believing her to be a child. Mona turns out to be a beautiful young woman, however, and Jim overnight stops drinking and chasing skirts, becoming a devoted family man. Killer Gordon, one of Jim's fighters, becomes friendly with Mona, and Jim, believing that she loves Killer in return, himself turns for consolation to his former mistress, Yvonne, whom he asks to marry him. She refuses, telling Jim that she is engaged to Killer; Jim is doubtful, and Mona, overhearing the conversation, runs to her room in tears. Jim follows and learns to his delight that it is he himself whom Mona loves.