The niece of Doctor Thorne, and illegitimate daughter of the doctor's late brother. Doctor Thorne takes in Mary after her father's death, but has kept her oblivious to the nature of her birth to be spared the public ridicule. She harbors feelings for her childhood friend, Frank Gresham (to whom the feelings are mutual), but the two are often kept apart by Franks mother Lady Arabella, who would prefer that her son marry into a wealthy family.