María and Manuel have a plan, or rather two: spend New Year's at the house of Manuel's sister and her partner, and take the opportunity to ask them for a very delicate favor.

Silvia and Andrés, two siblings who live with their grandfather in a house in the middle of the forest, unleash the wrath of a dark entity that will relentlessly pursue them until it catches them, during the course of one night. The children must use the entity's weaknesses to survive until dawn and get rid of the curse.