**SPOILERS** With things getting out of control in controlling the rowdy San Quentin inmates the prisons Warden Taylor, Joe King, gets tough but sensitive US Army man Capt. Steve Jamerson, Pat O'Brien, to replace the utterly incompetent and abusive Let. Druggin, Barton MacLane, as the commander of the prisons guards.
Steve meets, and falls in love with, Mea De Villiers aka May Kennedy, Ann Sheridan, at a San Francisco nightclub who's brother Red, Humphrey Bogart, later turns out to be a prisoner in the very prison that he's to be working at.
Working with, instead of against, the prison inmates has them stop their rebellious activities and at the same time respect Jameson. Let. Druggin, who's now Jamesons second in command, is planing to start up something by getting a number of inmates to break out in order to embarrass the guard commander and have him canned by Warden Taylor.
Red who's getting the hang of it in being cooperative with the prison administration, like Jameson want's him to, is later manipulated into going along with the hardened and murderous convict Carl "Sailor Boy" Hansen, Joe Sawyer,in a prison break secretly set up by Druggin.
Druggin having both Sailor Boy and Red put on a prisoner road work detail outside San Quentin the two plan is set up to escape by the two convicts with Sailor Boy's girlfriend Helen, Veda Ann Berg, being recruited to drive the getaway car.
The prison escape turns out to be a disaster for Druggin with him being kidnapped, instead of helped, by Sailor Boy and Red and later thrown from the speeding car to his death. With Sailor Boy killed in a car crash and Red then getting away from the perusing police by rail he later gets back to May's home in SF where he finds Jameson with her and then angrily basts him away.
Red mad at Jameson, for what he thought, taking advantage of May by treating him with kindness and understanding in the clink in order to make romantic points with her realizes, only too late, that both Jameson and his sister May were in love with each other. It turns out that Jameson somehow recovered for his wounds and survived Red's shooting.
With the cops outside May's apartment waiting for him Red tries to escape but is shot and fatally wounded. On the run and hitching a ride back to San Quentin, to give himself up, Red tells the guards in a kind of death bed confession that Jameson was right with what he did in the prison, in trying to straighten out incorrigible hoods like himself. Thus proving that Captain Steve Jameson's policies in San Quentin to have been right all along saving Capt. Jamesons job and his, Joeseph "Red" Kennedy's, troubled soul.
