While the holiday season represents the most magical time of year ancient European folklore warns of Krampus a horned beast who punishes naughty children at Christmastime. When dysfunctional family squabbling causes young Max (Emjay Anthony) to lose his festive spirit it unleashes the wrath of the fearsome demon. As Krampus lays siege to the Engel home mom (Toni Collette) pop (Adam Scott) sister (Stefania LaVie Owen) and brother must band together to save one another from a monstrous fate.