In the novel Why Didn't They Ask Evans?, Lady Frances "Frankie" Derwent is a plucky young woman. She is a friend of Bobby Jones. They solve a mystery together. She is the daughter of Lord Marchington, and has two brothers.
Lady Frances is also related to the Draycotts, acquaintances of Sylvia Bassington-ffrench.
Frankie Derwent stages a fake car crash near Merroway Court so that she could investigate the family living there.