The scene is a small Southern town where Colonel and Christine Penmark live with their daughter, Rhoda. Little Rhoda Penmark is the evil queen of the story. On the surface she is sweet, charming, full of old-fashioned graces, loved by her parents, admired by all her elders. But Rhoda's mother has an uneasy feeling about her. When one of Rhoda's schoolmates is mysteriously drowned at a picnic, Mrs. Penmark is alarmed. For the boy who was drowned was the one who had won the penmanship medal that Rhoda felt she deserved.