When the wealthy widow Madame Dauvray is found murdered at the Villa Rose in Aix-les-Bains, suspicion falls on her young companion Celia Harland, who has gone missing—along with Dauvray’s valuable jewels. The famous French detective Inspector Hanaud is called in to solve the mystery, which involves a séance, a missing chauffeur, and a web of deceit.

A. E. W. Mason was inspired to write this story after his own stay at an inn near London, where he saw the names of two victims of a famous murder scratched into a windowpane. Inspired by that case, he incorporated other small details from other murder cases into this narrative.