Inspired by true events. On an isolated stretch of land fifty miles outside of San Francisco sits the most haunted house in the world. Built by Sarah Winchester (Dame Helen Mirren) heiress to the Winchester fortune, it is a house that knows no end. Constructed in an incessant twenty-four hour a day, seven day a week mania for decades, it stands seven stories tall and contains hundreds of rooms. To an outsider it looks like a monstrous monument to a disturbed woman's madness. But Sarah is not building for herself, for her niece Marion (Sarah Snook), nor for the brilliant Dr. Eric Price (Jason Clarke), who she has summoned to the house. She is building a prison, an asylum for hundreds of vengeful ghosts, and the most terrifying amongst them have a score to settle with the Winchesters.