She is portrayed by Elizabeth Blackmore.
Mary is the daughter of Dr. Arthur Lydgate, who runs a prestigious academy that Mary's friend Henry Jekyll manages to get into by using Mr. Hyde to blackmail Arthur. Jekyll also falls in love with Mary, although when Mary does not reciprocate his feelings and falls in love with Hyde instead, Jekyll ends up becoming furious with Mary and a physical confrontation results in Jekyll pushing Mary out the window of her bedroom, where she falls to her death.
- Arthur Lydgate (father)
- She may be loosely based on Mary Reilly from the story of the same name, Mary Reilly.
- Mary's necklace ends up in Mr. Gold's pawnshop, until Hyde takes it back.
- S6, E04: "Strange Case" (flashback)