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. No sooner have the guests assembled than talk turns to the sinister Black Dudley Dagger and the ritual that accompanies this ancient relic. It all derives in 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... the host is discovered brutally slain. A murder always spoils a party, but the group soon find out that not only is there a killer in their midst, but the secluded house is under the control of notorious criminals. Trapped and at their mercy, George must find a way to thwart their diabolical plans while getting himself and Meggie out alive. Luckily for Abbershaw, among the guests is a stranger who promises to unravel the villainous plots behind their incarceration - but can George and his friends trust the peculiar young man who calls himself Albert Campion? He is a garrulous and affable party-crasher with a great knack for solving mysteries and interrogating suspects.