Five Little Pigs

Carla Lemarchant comes to Poirot with a letter her mother had written to her when she died, but had only recently come into her possession. Her mother, Caroline Crale, was 16 years ago convicted of the murder of her husband, accomplished artist Amyas Crale, and she died in prison a couple years later. In the letter Caroline claims she was innocent, a claim not shared by anyone who was actually closely connected to the crime, but one that Carla wants Poirot to help refute.