Joseph Marchwood was the son of Lord Marchwood. His sister Elizabeth Marchwood and he went looking for Erasmus Darkening. Once they had found him he was taken away and made into a ghost.
Joseph and his sister appeared in the 21st century and warned Sarah Jane Smith to "get out". She tried to help them but they walked off. After Sarah Jane and their father defeated Darkening, Joseph and his sister were reunited with their father as "ghosts". (TV: The Eternity Trap)
