Peggy Tregarth is convinced that an evil witch has cursed her. She runs to Penberth Cove to seek help from Granny Poldune, but finds that witches can cast their spells on anyone they choose, and it is Granny who has been chosen. Peggy must find the courage, through her love for Granny, to free her from the spell. With the aid of her best friend, Jimmy Wallace, Peggy risks her life to save Granny and to free the County of Cornwall from evil.