In Madrid, the boy Juan is terrified by the monster Hollowface and his mother is unable to protect him so summons Father Antonio to exorcise the monster from their lives. In London, the construction worker John Farrow is very close to his teenage daughter Mia. One day, Mia is spending the day at her grandparents’ house in the countryside with her mother Susanna and she finds a box with the story of Hollowface hidden in a tree. Soon Mia sees the monster Hollowface in the closet of her bedroom and John defends her. When they are attacked for the second time, the security camera that John has installed does not show any intruder. Are Mia and John delusional?