Sneed believed his house was haunted, since the corpses refused to stay dead. He and Gwyneth went to the Taliesin Lodge in Cardiff to find Mrs Peace, whose corpse was possessed by a Gelth. They retrieved her and captured Rose Tyler, who had seen them taking Mrs Peace into their hearse, and took them to Sneed and Company.
The Ninth Doctor and Charles Dickens followed and they soon learned what was going on. Sneed and the others performed a séance. The Gelth told them they were trapped behind the Rift and had become creatures of gas. In the morgue, Sneed was killed and his dead body was subsequently possessed by the Gelth, who wished to take over all of humanity's bodies. (TV: The Unquiet Dead)
Behind the scenes
The part of Sneed was originally written for David Tennant. When Tennant was first told of the change in role at the last minute from Gabriel Sneed to the Tenth Doctor, he believed it to be a joke. (REF: Doctor Who: The Inside Story)