The Black Dudley is an ancient, remote mansion inhabited by recluse, Colonel Combe, but owned by Waytt Petrie, a young academic who decides to revive his property with a weekend party to which he invites his friends and colleagues. Among the guests is George Abbershaw, a renowned doctor and pathologist who is occasionally summoned by Scotland Yard to help with consulting mysterious deaths. Abbershaw hopes that the leisurely weekend at Black Dudley will help him to get acquainted with red-haired Meggie Oliphant whom he quietly admires. Little does he suspect that instead he will be involved in a series of extraordinary and dangerous incidents which unravel one by one in the gloomy mansion and split the party.

It all begins with a seemingly innocent ritual-game, played in Black Dudley for generations, in which a jewelled dagger is passed between the guests in the darkness. The young visitors are intrigued and eager to play, but when the lights are restored it becomes apparent...