One rainy night, Dr. Garondet is summoned to the castle of Professor Orloff. Making it to the castle on foot, the good doctor meets Cecile, Orloff's daughter, a seemingly deranged girl who is convinced that an invisible phantom is at large on the premises. Orloff explains the story behind Cecile's insanity to the doctor--a tale involving premature burial, grave-robbing and flagellation--and invites him to stay over. As Garondet spends an uneasy night at the castle, he finds himself sharing in Cecile's delusions.