Tommy McCoy, a quick-fisted, tough New York City youth, sells newspapers and wages bets in pool halls to help support his parents. Tommy's father Brian, an unemployed vaudevillian, believes his career in show business is finished until he is asked by Father Ryan to perform at the neighborhood association's boxing match. Though offered only ten dollars for his performance, Brian gladly accepts the invitation, and asks Tommy to perform a song-and-dance routine with him. At the event, Tommy enters the boxing ring, challenges champion fighter Danny Burns and wins the fight in a knockout. Tommy's boxing prowess impresses lightweight champion Johnny Martin, who invites him to learn more about fighting by joining his traveling boxing tournament as an entertainer. Tommy and Brian become successful on the road, but their joy is dampened when Brian receives word that his wife has died. Tommy and Brian continue to perform in Johnny's traveling show, and their association with Johnny continues until the champion fighter retires from the boxing ring. Tommy takes over for Johnny in the ring and becomes an instant sensation, scoring one victory after another. Meanwhile, Brian, who has been drinking heavily and squandering his and Tommy's money, amasses a large gambling debt. One day, Tommy learns that he is set to fight Johnny, who is attempting a comeback, and refuses to fight him. However, Tommy is compelled to accept the challenge to make enough money to pay his father's $600 gambling debt to Jim Caighn. In the ring, Tommy takes it easy on Johnny, but the former champion, out of practice, is killed by a light punch. Tommy is devastated by the accidental death and decides to quit boxing. He is forced to continue, however, when he learns that his father has sold his contract to Caighn. Determined to make enough money to buy back his contract, Tommy agrees to fix his fights to help the gambler bankrupt his rivals. Tommy and Caighn profit handsomely from the scheme, but when a romance flourishes between Tommy and Caighn's daughter Sheila, Caighn warns the fighter to stay away from her. On the eve of Tommy's big fight against Patsy Cigones, Brian in a drunken stupor, tells Caighn's rivals that Caighn has been secretly managing Tommy's career and that all of Tommy's fights are rigged. Having bet heavily on Tommy's opponent, Caighn's rivals kidnap Sheila, hold her and Brian hostage and threaten them with harm unless Tommy takes a fall in the eighth round. As the fight approaches the eighth round, Brian overpowers his captors and sends Sheila to the boxing arena to prevent Tommy from taking his fall. Though Brian is killed by his captors, Sheila arrives at the arena in the middle of the eighth round, and her presence inspires Tommy to defeat his opponent with a knockout punch. After the fight, Caighn promises to reform and gives Tommy and Sheila his blessing to resume their romance.