Dr Louise Mortimer is Henry Knight's psychologist, who he hired to help him overcome the memory of the events of his father's death when he was just a child. On her advice Knight returns to the Baskerville area to try to piece together his memories. She is seen through out the episode counselling Knight which seems to work, and helping him remember more details about the events of his father's death. Watson approaches her in order to gather information for the case but is ultimately derailed when Dr Frankland blows his cover.