Luna, the cabin manager's assistant, leaves Aníbal and Barakaldo in charge of three tenants who are staying for the weekend to celebrate Christmas together. Despite the clumsy duo's desperate attempts to make everything go well, things get out of control when the three friends read a spell book that summons very aggressive and very short monsters.

A dysfunctional family made up of Saioa, a submissive mother, Gorka, the teenage son, and Andoni, the abusive father, reveal their most extreme side when they travel to the cabins of Mount Amboto. Everything gets worse when they are attacked by a car that comes to life and destroys everything in its path. What they don't know is that the car isn't going to be the only horrible thing that happens to the family.

After much effort, Koldo finally manages to steal La Piedra de Mor and the spell book from the huts of Mount Amboto. As he is about to escape, the Stone releases an extremely powerful enchantment on one of the cabins that forces Luna, Zigor, Hannibal and Barakaldo to solve a dangerous riddle while fighting against their deepest fears and to save their own lives.