One Christmas, a woman tells her granddaughter, Zoe Weaver, about Krampus. Zoe is placed in foster care after the death of her parents, and is eventually adopted by an abusive couple, who she kills using homemade, Voodoo doll-like effigies that can bring forth Krampus. While at a hospital, Zoe is interviewed by a child psychologist named Rachel Stewart, and uses her dolls to summon Krampus to murder a pedophilic orderly, as well as the negligent, alcoholic father of a fellow patient named Ashley.