When Adam Bingham's grandfather dies, the family gathers at the farm for the reading of the will and a proper wake. Unfortunately, that means the deceased's sister Agatha - called Hagatha behind her back - will also be in attendance. While Hagatha proceeds to torment everyone she comes in contact with, it becomes clear that drastic measures are needed to put a stop to her. So as Adam plots Hagatha's demise with his cousins, he finds an unexpected ally in Grandpa Lum's peculiar neighbor, December Ashby, and brokers a tenuous peace with Sauerkraut, the feral barn cat. Hell breaks loose when Hagatha is discovered dead in the cellar and Adam's dysfunctional family falls under the scrutiny of local law enforcement, which is convinced that Hagatha died under suspicious circumstances. Adam soon learns that he and December are top of the suspect list, and that when such unspeakable evil comes a-calling, murder is best kept a family affair.