Five Little Pigs

Beautiful Caroline Crale was convicted of poisoning her husband, but just like the nursery rhyme, there were five other "little pigs" who could have done it: Philip Blake (the stockbroker), who went to market; Meredith Blake (the amateur herbalist), who stayed at home; Elsa Greer (the three-time divorcEe), who had her roast beef; Cecilia Williams (the devoted governess), who had none; and Angela Warren (the disfigured sister), who cried all the way home.
Sixteen years later, Caroline's daughter is determined to prove her mother's innocence, and Poirot just can't get that nursery rhyme out of his mind.