In the novel Five Little Pigs, private investigator Hercule Poirot uncovers the real killer in a fifteen-year-old murder case. Poirot was contacted by the daughter of Caroline Crale to re-investigate a murder for which Carolin was convicted. Caroline's daughter, Carla Lemarchant, had a letter from her mother claiming her innocence. Carla also wanted proof so that she could marry without fear that she might harm her own husband-to-be. The novel deals with themes of psychology, emotionality, rationality, guilt, and lifestyle.