Scheduled for execution, a serial killer in a psychiatric evaluation claims to be a demon and predicts the psychiatrist will commit three murders before their time ends.

A notorious serial killer, Edward Brady, is facing execution at 11pm. Dr. James Martin is brought in to replace Dr. Alan Fischer who committed suicide after interviewing Edward. Edward's fate now depends on Martin's diagnosis. If Martin decides that Edward is sane, he will be executed, but if he declares him to be insane, Edward will be spared. "Edward" claims that he is possessed by a demon named "Nefariamus", and also says that Martin will commit three murders by day's end.

Martin initially dismisses Edward's claims, but as the demon's knowledge of Martin's life proves uncannily and disturbingly accurate, Martin's skepticism begins to fade. The weight of Nefarious' claims both frighten him and fill him with self doubts. With Edward's fate hanging in the balance, Martin must make a fateful decision based on his professional diagnosis, while grappling with his personal feelings of fear and disgust, and the conflict of interest they create.