Having a child destroys your immune system to horror, real or imagined. As surely as Pan’s Labyrinth—whose director, Guillermo del Toro, served as producer here—this eerie Spanish-language shocker seems designed to lay open a parent’s worst fears, both of a child in peril and a child as threat. At a gloomy Gothic orphanage converted into a children’s clinic, a former resident (Belén Rueda) grows worried over her little boy’s new stable of imaginary playmates. Then the boy vanishes—and his distraught mother must turn to the household’s invisible tenants, to solve not just his disappearance but theirs. Directing his first feature, J.A. Bayona overdoes the slasher-movie music stingers and shock sound effects, but on the whole this is a worthy addition to the classy Spanish horror cinema of recent years, mixing haunted-house atmospherics with tooth-rattling jolts. And the excellent Rueda, wandering the empty house in jittery despair, gives as gripping a screen solo as Will Smith in I Am Legend—the season’s other ice bath in the isolation of parental grief.