A teenage girl is raised underground by a kindly robot "Mother" -- designed to repopulate the earth following the extinction of mankind. But their unique bond is threatened when an inexplicable stranger arrives with alarming news.

When his dysfunctional family clashes over the holidays, young Max (Emjay Anthony) is disillusioned and turns his back on Christmas. Little does he know, this lack of festive spirit has unleashed the wrath of Krampus: a demonic force of ancient evil intent on punishing non-believers. All hell breaks loose as beloved holiday icons take on a monstrous life of their own, laying siege to the fractured family's home and forcing them to fight for each other if they hope to survive.