Uncle Gregory is found with a knife in his back and “blackmailer” as his epitaph. Only Miss Maud Silver can solve the crime.
When the menacing Gregory Porlock invites a group of unacquainted friends to his home, the house party takes on a sinister edge. The host himself is stabbed in the back, and it becomes clear to all that he was a blackmailer. But who thrust the fatal knife is up to Miss Silver to discover.