When Caroline Ames makes the daring decision to visit a medium, she keeps it a secret from her older brother, Addington. Ever the rationalist, Addington has made his disapproval of Boston society's recent infatuation with spiritualists quite clear. Fervently hoping to contact their mother, Caroline has asked Dr. MacKenzie, the Ameses' boarder and dear friend, to accompany her to a seance held by Mrs. Sidgwick, reputed to be the best medium in Boston. Mrs. Sidgwick's powers prove to be quite amazing: Although she is unable to reach Mrs. Ames, she miraculously fulfills the expectation of others attending the seance. Among them is Theophilus Clay, a well-known and much-beloved philanthropist who receives a message from his late wife - and is immediately struck dead right in Mrs. Sidgwick's parlor.

Addington agrees to help clear Mrs. Sidgwick's name but needs more solid proof before he is willing to accept Mrs. Sidgwick's connections to Clay's murder.