Capt. Barnaby (Edward G. Robinson), leader of the Los Angeles Vice Squad, is trying to track down the murderers of a beat cop. To do this, he pulls some strings to coerce help from Mona Ross (Paulette Goddard), the madam behind a local escort ring. Using this lead and further help from an informant, Barnaby hunts down a pair of bank robbers he suspects are the killers. However, the criminals prove to be hard to catch, so Barnaby must stay determined.