In a sprawling mansion in the affluent suburb of Swinly Dean, Aristide Leonide lies dead from barbiturate poisoning. His cunning widow, 50 years his junior, is set to inherit a sizable fortune, and is rumored to be carrying on with a strapping young tutor living on the estate. But criminologist Charles Hayward casts his own doubts on the innocence of the entire Leonides brood. He knows them intimately — and knows no one is on the level.