Bess Southerns, an impoverished widow living in Pendle Forest, is haunted by visions and gains a reputation as a cunning woman. Drawing on the Catholic folk magic of her youth, Bess heals the sick and foretells the future. As she ages, she instructs her granddaughter, Alizon, in her craft. When a peddler suffers a stroke after exchanging harsh words with Alizon, a local magistrate, eager to make his name as a witch finder, plays neighbors and family members against one another until suspicion and paranoia reach frenzied heights.