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!