Near the end of World War II, American soldiers perpetuate an unspeakable horror on a local nun. Turned away from the church, Krampus hears her cries, enacting brutal revenge - but it comes with a price. Decades later, two sisters visiting Europe on Christmas holiday are unexpectedly plunged into the nightmare web of Sister Krampus, bride to the holiday deity. They are aided by a local village woman, and together they venture into the nearby, desolate convent to unlock the secret to stopping the evil spirit once and for all.
