Brain-worm

A  was able to eat people's minds. It followed the telepaths, Tessa Waylund, Gorden Latch and Jane Thirgood, as well as Charlotte Pollard around the Cube and captured the Eighth Doctor and C'rizz. It took part of the Doctor's memory. No one had physically seen it. It was created by a faulty experiment, when trying to remove Tessa's psi powers. It originally resided in Tessa's mind, then transferred to the Doctor's, and then into Latch's. (AUDIO: Something Inside)