Plague Court is old and crumbling, long neglected after its lord, hangman's assistant Louis Playge, fell victim to the black death centuries before. The estates is famously haunted by Playge's ghost. The new owner hires an exorcist to banish the ghost, but the exorcist is found stabbed to death in a locked stone hut on the grounds. Sir Henry Merrivale, an amateur sleuth, investigates whether the violence is supernatural-- or of a much more human cause.