Castle and Beckett investigate the murder of a ghost hunter named Jack Sinclair who was looking into a haunting at a New York mansion. As they delve deeper into the case, Castle supports the idea that supernatural powers could be at work, while Beckett looks for a non-supernatural reason for the murder. While looking at the haunted mansion, Castle and Beckett discover a secret alcove where the killer killed Jack Sinclair, putting Castle's "demon" theory to rest.
- Agent Mulder: Castle and Ryan.
- Engineered Public Confession: Beckett and Castle lures Jack's killer, Smith into one.
- Hypocrite: Smith mocks the people who believe in demons and superstition but after getting arrested, he pleas that he was controlled by demons to kill.
- "Scooby-Doo" Hoax: Detective Smith has been pulling one of these in order keep anyone from finding the body of Fuller in the hidden room.
- Trauma Button: Jack chose the haunted house because he remembered that someone died there.
