The story begins in 1950 with a murder in a remote Cornwall village. A cryptic message is discovered on the victim and the case is assigned to newly-appointed DI Harry Dillon of Scotland Yard. The mystery looks impossible at first with few clues and hidden names and disguises. All is not what it seems and two more murders follow the first. Dillon colludes with his friend, Jim Wilson-Smythe, and their two sisters as well as Harry's neighbour. Between them, they uncover terrible crimes and solve the intriguing case.