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.
A young doctor visits the castle of an insane scientist. He has heard from the warnings of the villagers that the scientist is conducting strange experiments, and in true horror movie fashion, decides to investigate. The scientist's daughter seems to be tormented by the vision of an invisible phantom, and as the young doctor stays on, he too begins to experience the terror. Is the phantom only in their minds, or is it the creation of the scientist' Who would be mad enough to create an invisible monster'