Who killed Charmian Karslake, the famous American actress, on the night of the ball at Hepton Abbey? Who was the mysterious Peter Hailsham who had been present at the ball and had since vanished into thin air? What was his connection, if any, with the respectable County family of Penn-Moreton at whose house the murder had taken place? How Inspector Stoddart and his assistant Harbord solve these questions, and the surprising discoveries they make in the course of their Investigations, form the basis for one of their most devilish mysteries.