Bill Knight is disappointed when he receives his first assignment as a newly inducted policeman, fresh from college. He is asked to go undercover in a festering slum and is ordered not to set foot in police headquarters again until a thoroughly distasteful mission has been accomplished.

So Bill becomes a plainclothes spy, and things take an even more complicated turn than anyone could have expected when he becomes involved with two girls while investigating the murder of a pub landlord and the theft of a valuable coin collection.