Mary, Lady Stewart (born Mary Florence Elinor Rainbow; 17 September 1916 – 9 May 2014) was a British novelist who developed the romantic mystery genre, featuring smart, adventurous heroines who could hold their own in dangerous situations. She also wrote children's books and poetry, but may be best known for her Merlin series, which straddles the boundary between the historical novel and fantasy. Adaptations of her books include both The Moon-Spinners: a Walt Disney live-action movie, and The Li…