Dennis Rafkin (Matthew Lillard) is a supporting character of Thirteen Ghosts (2001). He is a powerful, yet neurotic psychic, but his only powers are feeling ghosts, commonly going into seizures or getting what seems like insanely painful neck and head pains, and seeing people's lives, past, present, future, flash before his eyes when touched or touches someone.
He has helped Cyrus Kriticos capture all the Ghosts, but he never knew what exactly for, he did try and attempt to find out what Cyrus was doing when capturing the last ghost, The Juggernaut, but only caught two small glimpses of a machine, before Cyrus broke off the contact, telling Dennis not to get too curious. Dennis refused to help Cyrus after Juggernaut's capture and wanting the money he was promised, which sounds to be a lot.
After meeting Arthur, he discovers unintentionally that the 4th Ghost, The Whithered Lover, is Jean Kriticos, Arthurs wife, but remains silent about it until Cyrus's secret lover and lacky, Kalina, tells Arthur.
Once understanding that Cyrus was just using him to capture the ghosts and that the house is a machine to open hell, something to him doesn't make sense at Arthur sacrificing himself to the eye in order to save his children. Dennis requests that he and Arthur venture out one more time to find out more clues, this time, taking a protected glass piece from the study with them.
While on their way, Dennis realizes that The Hammer is close by and uses the glass to trap Arthur in a corner, his last words to Arthur was that he had been looking to find a reason for liking himself. He confronts The Hammer, but only to suddenly realize that the Jaggernaut was out, sacrificing himself for Arthur.
After Cyrus is killed by the Ghosts, he tells Arthur that it's not over just yet and to go to his kids. After the destruction of the house, Dennis smiles and disappears.