Los Angeles, post WWII, a criminal shots and kills a police officer in the middle of the night. Without any leads, the chief of the LAPD assigns Sgt. Chuck Jones and Sgt. Marty Brennan to investigate. When the dealer of electronics devices, Paul Reeves, is caught selling a stolen projector, the police identifies the criminal. Witnesses of the heists give descriptions of the man, but his true identity remains unknown.