Spanish-language horror movie in which the children of a family on vacation in Tijuana begin exhibiting bizarre and frightening behaviour. Felix (Francisco Barreiro), Sol (Laura Caro) and their children, Adolfo (Alan Martinez) and Sara (Michele Garcia), are on a trip to some caves when their troubles begin. When the children beg to go and hike a nearby hill before they leave, their parents agree to let them do so, happy that they will be able to spend some time alone. However, when Adolfo and Sara fail to return before nightfall, Felix and Sol are naturally distressed, calling the police and spending a miserable night in a motel awaiting news. When the children reappear the next morning they are delighted but puzzled and troubled by their subdued and erratic behaviour. Felix and Sol presume that the children were sexually abused in their absence, but have they encountered darker forces still?