Sarah Winchester is the widow of famed Winchester Arms William Wirt Winchester. Her husband's sudden death and the previous death of their child Annie have left her in grief. Having received more than twenty million dollars in inheritance, Winchester convinces herself she is cursed by the ghosts of those who died at the hands of Winchester firearms. After seeking advice from a Mediumship, she begins building an enormous, seemingly never-ending mansion in San Jose, California that would eventually be named the Winchester Mystery House. The house is under constant construction and Sarah's niece Marion Marriott lives in the house with her son Henry. At night, Henry is possessed by a mysterious entity.