Ex-Army officer Steve Jameson (Pat O'Brien) becomes the chief guard at San Quentin State Prison following riots that protested harsh punishments given by the former chief guard, Lieutenant Druggin (Barton MacLane). While celebrating at a nightclub, Steve meets singer May Kennedy (Ann Sheridan) and they are drawn to each other. May's younger brother, "Red" (Humphrey Bogart), bursts into the nightclub where he is arrested by the police for bank robbery. Since the arrest is not his first offense, he is sent to San Quentin, where he fights hardened criminal "Sailor Boy" Hansen (Joseph Sawyer) on his first day. When May visits, she finds out that Steve is the chief guard and, believing that Steve is subjecting Red to harsh treatment, ends their relationship. In fact, Steve is trying to improve conditions by separating hardened criminals from other inmates, despite opposition from the prison board and Druggin. Steve wins over Red with his improvements, such as assigning Red to a road crew outside the prison. But Druggin assigns Hansen to the road crew as well and Hansen recruits Red to join an escape plan. Red refuses, but Hansen convinces Red that Steve is only treating him well to reunite with May. Enraged, Red agrees to the escape plan. Red and Hansen escape the road crew and take a guard hostage, but Hansen is killed in a crash. Red goes to May, but Jameson is also there, and a confrontation is inevitable.
—Patrick Depew