Ned Talbot

 was a spiritualist. He was sent for by Maurice to look for the ghosts of the soldiers of World War I. He said that he wasn't a fraudster and told the Fourth Doctor about why he did his work. He conducted a seance where a child scream was heard. When the Doctor disappeared, he thought it was unheard of the spirits taking something physical. He discovered spiritualism after his son died in the Boa conflict. (AUDIO: The Haunting of Malkin Place)