Susan Ertz (13 February 1887 – 11 April 1985) was an Anglo-American writer, known for her "sentimental tales of genteel life in the country." She was born in Walton-on-Thames, Surrey, England to American parents Charles and Mary Ertz. She moved back and forth between both countries during her childhood but chose to live in England when she was 18. She married British Army soldier, Major John Ronald McCrindle in London in 1932. A common theme running through her work involves a female character "who is thrust out on her own from a sheltered environment into a vaguely hostile external world with which she is initially unprepared to cope. Her coming to terms with this hostile world provides the fictional interest of [her] novels." The Proselyte, the story of a London woman who marries a Mormon missionary and moves with him to Utah, was one of her most highly praised books (even Mormons felt that in "her story the hardships and sorrows of the people are clearly portrayed"). Ertz's Woman Alive is a science fiction novel set after all women other than the titular heroine have perished in a plague.One of her later works, In the Cool of the Day, was the source of an eponymous movie in 1963, starring Jane Fonda, Peter Finch, and Angela Lansbury.