Lefty O'Brien, a pugilist, becomes engaged to ex-tomboy Patsy Ryan against the wishes of her father, Michael. They both live in an Irish-Jewish neighborhood on New York's East Side known as "Hogan's Alley." Lefty defeats Battling Savage for the championship, breaking his left hand and leaving his opponent close to death. Lefty seeks refuge from apprehension by the police, but Michael turns out both Lefty and Patsy. Patsy is injured, and Michael calls in wealthy Dr. Emmett Franklin, who takes more than a professional interest in Patsy. He invites Michael and Patsy to a dinner that turns into a wild party. Lefty breaks in, and Patsy returns his ring. The doctor invites father and daughter to his mountain lodge, but he leaves Michael stranded at the station. Michael and Lefty pursue the train in an automobile. The car and train collide, and the engineer abandons the train, leaving a part of it to run away. Lefty rescues Patsy with the aid of an airplane; the two settle down to married life and, to Michael's pleasure, make their fortune in plumbing.