Classic British mystery thriller starring Tom Conway as suave gumshoe, Norman Conquest. After intercepting a secret message, Conquest meets foreign femme fatale, Nadina Rodin (Eva Bartok), in room 605 of the Park Plaza hotel. When Conquest wakes up in the room the next morning he is lying next to a corpse and the mysterious Rodin is nowhere to be seen. Conquest is now the police's number one murder suspect with Inspector Williams (Sid James) shadowing his every move. In order to clear his name, Conquest enlists the help of Pixie Everard (Joy Shelton), but things turn even uglier when he discovers that the murder is connected to a stash of stolen diamonds. As gun-toting, trigger-happy gangs of communists and sinister Nazi sympathisers enter the frame, Conquest has to solve the murder whilst staying one step ahead of both the bad guys and the boys in blue.