"The Witchfinder's Sister" is a historical novel by Beth Underdown set in 17th-century England during the English Civil War. The story follows Alice Hopkins, the sister of the infamous witchfinder Matthew Hopkins, as she navigates the dangers of a society gripped by fear and superstition. As Alice becomes increasingly aware of her brother's brutal methods, she struggles with her loyalty to family and her moral convictions. The novel explores themes of power, gender, and the impact of hysteria on communities, providing a gripping portrayal of a dark chapter in history.