Halloween is a time for children to go door to door trick-or-treating. For Doyle and his girlfriend, Poppy, it's a time to catch a ghost. Poppy is investigating an insurance claim of a woman who says she was pushed down a flight of stairs by a ghost in a posh but very old hotel in Detroit. She enlists Doyle to help, and they try to get to the bottom of the claim.
The hotel manager is frantic to disclaim the woman, since it's now a lawsuit, and the woman is staying in the hotel until they can settle. Doyle and Poppy search the hotel for clues, but they have to wait an extra day before they can get into a mysterious room with a door that just won't open. While waiting for help to get into the room, they go up to Doyle's newly rebuilt cabin, and while in town they are given a request to exorcise a demon. Only the demon is something Doyle never expected.
Back at the hotel, they wait for the ghost of a woman who hanged herself years ago and prove she doesn't exist. Murder, ghosts, demons, and psychics are just a few of the Halloween treats and tricks they have to face. This is the fifth book of the Doyle, P.I. series.