The film follows Steve Lacey, a reformed parolee trying to live a clean life with his wife Ellen in Los Angeles. His past catches up to him when three San Quentin escapees, led by "Doc" Penny and including a young thug named Ben Hastings (Charles Bronson), kill a police officer during a gas station robbery and seek refuge at Steve's home. 

Caught between the hardened, cynical Detective Lieutenant Sims (Sterling Hayden), who believes "once a con, always a con," and the desperate demands of the escapees, Steve is forced to participate in a bank heist to protect his wife, who is held hostage. The film is known for its gritty, realistic location shooting around Los Angeles and its intense, fast-paced rhythm.