Ghost janitor

Recently I ran a one-shot RPG, where the players were a team of paranormal investigators and freelance exorcists. The story was heavily inspired by Ghostbusters, old vampire-flicks, The Frighteners and Supernatural. The team were hired to get rid of a poltergeist haunting the fanciest hotel in Boston, the ghost of an Irish janitor who had died there in the 1920's. The restless spirit was defeated but revealed to not be the main danger haunting the place, which had turned an otherwise harmless spirit into a raging beast.