Marion was able to somehow leave her body and hurt other patients, of whom she was jealous because they often had family members visit them. Whenever she used this ability, a rash would appear on her abdomen.
She was visited by the Third Doctor and Jo Grant. He told her that something evil was feeding on others to make her stronger. When she tried to hurt the Doctor, the rash on her abdomen took the shape of time equations. After some time, she died of her illness. (PROSE: Angel)