London, 1974. As Britain prepares for electrical blackouts to sweep across the country, trainee nurse Val (Rose Williams, Sanditon) arrives for her first day at the crumbling East London Royal Infirmary. With most of the patients and staff evacuated to another hospital, Val is forced to work the night shift in the empty building. Within these walls lies a deadly secret, forcing Val to face her own traumatic past in order to confront the malevolent force that's intent on destroying everything around her.