In the novel Hallowe'en Party, Nora Ambrose was a teacher at The Elms school at Woodleigh Common. She was a close friend of another teacher Janet White with whom she shared a flat. After Janet was found strangled some two and a half years before the events in the book, Nora, who was higly upset, left the school and moved to another post in the north of England.
Elizabeth Whittaker, a teacher at the school told Poirot that Nora and Janet White were "over-sexed" but in different ways. She was unwilling to elaborate.