Susan Ertz was born in Walton-on-Thames, Surrey, England, to American parents. Her childhood was split between the United States and England, but at the age of eighteen, she chose to settle permanently in England. In 1932, she married Major John Ronald McCrindle, a British Army soldier, in London. Her dual heritage and transatlantic experiences heavily influenced her perspective as a writer.
Ertz became known for her "sentimental tales of genteel life in the country." A recurring theme in her fiction is the journey of a sheltered female protagonist who is suddenly forced into a hostile or unfamiliar external world. The narrative focus of her novels typically centers on how these women adapt, grow, and learn to cope with their new realities.
Among her most acclaimed works is The Proselyte, which details the struggles of a London woman who marries a Mormon missionary and relocates to Utah. The novel received praise, including from the Mormon community, for its realistic portrayal of the hardships faced by settlers. Ertz also ventured into speculative fiction with Woman Alive, a science fiction novel about the sole female survivor of a global plague. Her later novel, In the Cool of the Day, was adapted into a 1963 feature film starring Jane Fonda, Peter Finch, and Angela Lansbury.
