Famous investigator Harry Dickson is just back in London after some well-deserved holidays, and already Scotland Yard are seeking his help again, for there are very strange events afoot. A famous heiress and writer, Delphina Cruikshank, has vanished from a locked house. The corpse of an executed murderer has disappeared while the doctor who was autopsying him was murdered. And Mysterion, Miss Cruikshank's new character, may not be entirely fictional!