London - the long, hard Winter of 1974. As striking miners switch off the power across Britain, rolling electrical blackouts plunge the country into darkness. Val, a young nurse on her first day of duty, is forced to work the night shift in a crumbling hospital.
When most of the patients and staff are evacuated to another hospital across town, Val finds herself in a near empty building, enveloped by a sinister darkness. Within these walls lies a deadly secret and a terrifying presence. Now Val must face her own traumatic past and deepest fears to confront the malevolent force intent on destroying them all.