A physics professor gathers a group of Ph.D students to help him conceive a poltergeist in this Hammer Films production based on actual events. Jane Harper (Olivia Cooke) is a deeply troubled girl possessed of an all-consuming blackness, and Professor Joseph Coupland (Jared Harris) has a particularly unconventional plan for getting the darkness out of her. Summoning his top students to a secluded estate on the outskirts of London, Professor Coupland proposes that they attempt to manifest the malevolent energy in Jane. What the brilliant instructor and his ambitious students discover when they attempt to do so, however, is a horror so unrelentingly baleful and powerful that it may destroy them all before they even realize what a terrible mistake they've made.