Libby Day is a lifeless woman who survived the massacre of her family in their farmhouse in the countryside of Kansas when she was eight. She's been living on donations and lectures ever since. Thirty years ago, the police believed that a satanic cult was responsible for the murder of her mother and two sisters, and her brother Ben was convicted with her testimony in court. Today, however, an acquaintance, Lyle Wirth, invites Libby to visit "The Kill Club", where amateurs investigate famous crimes, and she finds that they believe Ben is innocent. Libby needs money and, in return, accepts to revisit the slaughter of her family and comes up to the painful revelations and the ultimate truth.