Into The Light (Joe Cavelli, Paranormal PI)
Max Paddington refuses to go into the light until he finds his killer. This presents a dilemma, since Max is even less competent as a spirit than he was as a live person. No one sees or hears him and he can't manage to get anywhere or do anything on his own.
Joe Cavelli is a private investigator, living an ordinary life. Then one day he walks across a parking lot, gets yelled at by a ghost, and his life only gets stranger from there.
Max and Joe team up to find Max's killer. In the process, they form an unlikely friendship and change each other's lives in ways they never expected.