Orla and her husband, Nick, move into an antiquated Georgian house on the Dorset cliffs. But as they settle into the mansion --- Nick absent all week, commuting to the city for work --- Orla finds herself unsettled. She hears voices when no one is around; doors open and close on their own; and her son Sam, who has not spoken in six months, seems to have made an imaginary friend whose motives Orla does not trust. Four decades earlier, Lydia moves into the same house as a live-in nanny to a grieving family. She, too, becomes aware of intangible presences in the large house and becomes increasingly fearful for the safety of the children in her care. Are both families careening towards tragedy? Are Orla and Lydia seeing things that aren’t there? What secrets is the house hiding?