In 1925, at her family's suburban Philadelphia estate, 13-year-old Emily Stewart discovers she can make a loud rapping noise with her ankle. With her sly twin brother, Michael, Emily entertains gullible schoolmates with "knockings" that spirits purportedly make to answer questions about the afterlife. When adults who have suffered the loss of loved ones start consulting her as a spirit medium, her efforts to give them consolation begin to seem increasingly like cruel deceptions. Based loosely on true events from the early 20th century.