As the holiday season approaches, a dysfunctional family comes together to celebrate Christmas. Among them is young Max, who still harbors a belief in Santa Claus and the Christmas spirit, despite the family's bickering and cynical attitudes. Max's faith in the season is tested as tensions reach a breaking point, leading him to tear up his letter to Santa in a fit of disillusionment. The shredded wish list is carried away by the winter winds, unwittingly summoning a dark force.

The family's lack of festive spirit unleashes the wrath of an ancient, malevolent entity. As a severe blizzard encases their neighborhood, the relatives find themselves trapped and increasingly terrorized by strange occurrences. Ominous signs manifest as they come face to face with the twisted holiday lore they have dismissed. Meanwhile, Max's grandmother harbors knowledge of the sinister figure behind the chaos, hinting at a deeper folklore that turns the holiday upside down.