This is another in the spate of semidocumentary crime films which appeared in the late 1940s (HOUSE ON 92ND STREET, NAKED CITY, etc.). Stevens is an undercover FBI agent who investigates after a woman is killed in the holdup of a nightclub. The chief suspect in the case is arrested,
bailed out, and murdered, and the FBI soon learns that he was framed. Stevens is given the identity of a drifter and sent to hang out at a gym where he meets Widmark, a promoter. Later, when his wallet is stolen and then recovered at the scene of a robbery, he is arrested and taken to jail but is
soon out on bail posted by Widmark. He is inducted into Widmark's gang and learns the plans...