Hal Donovan gets into a fight with ex-heavyweight champion Slug Cassidy at a lumber camp in the north woods. Slug takes a bad beating and he and his trainer, Spider, urge Hal to become a professional boxer. Soon, "Chopper" Hal proves to be a natural and is beating all comers. He meets Kay Conrad, who is struggling to support her father, an ex-fighter invalided for life in the ring, and her young brother Dickie. Kay hates everything connected to the sport, and Hal keeps her ignorant of his profession. But Slug and Spider tell the Conrads of Hal's identity as "Chopper" Hal, and Kay breaks off the engagement while Hal takes to the open road. Hal, now a tramp, picks up odd jobs where he can find them and one of them leads him to a training camp where he meets Slug and Spider with their new fighter Lion Lee. He also meets Kay and learns that her father is in desperate need of money. He accepts Spider's offer to fight Lee, on the condition that he take a dive in the third round. Kay learns ...