Clumsy, put-upon Ruth Patchett leads a drudge's life with her two bratty children Nicola and Andy, and her neglectful accountant husband Bobbo. When Bobbo starts an affair with his top client, the glamourous, lighthouse-dwelling romantic novelist Mary Fisher, Ruth does everything she can to be a good wife but everything fails and Bobbo humiliates her in front of his parents before leaving her for Mary. Ruth snaps and, declaring that she will become a she-devil, burns the house down in such a way that the insurance claim will be invalid and dumps the children on Mary and Bobbo.