Based on a true story: Mary Roff, age 19, died in 1865 after being diagnosed insane for appearing to assume strange personalities, including a German-speaking one. Thirteen years later a 13-year-old girl named Lurancy Vennum begins to exhibit the same symptoms, and calls herself Mary Roff. Mary's father is recognized by the 13-year-old Lurancy, and thus begins the strangest case of possession.