When newly retired headmistress, Harriet Quigley, needs a good rest and somewhere comfortable to recover from a hospital stay, she believes Firstone Grange will be the ideal place. Luxurious and perfectly run by a competent and understanding matron, it seems wonderful at first glance. However, there is a serpent in this paradise and Harriet soon realizes that some of the residents are very frightened. When a particularly horrific death occurs and Harriet finds herself in danger, she calls on her cousin and best friend, the Rev'd Sam Hathaway, and together they attempt to discover the terrible truth...