Paula and her husband find a girl wandering on the main road of the town where they live. Two weeks later, after seeing that no one claims her, the two decide to temporarily let her live at their house. But it won’t be that easy, since the girl lives obsessed with the fantasy that a monster will come out and punish her if she ever steps out of a chalk square painted on the floor. After the strong bond created between the two, Paula sets off on a dark path to try to uncover the girl’s enigmatic past.