Revelation of Ratchett's Identity

Using a spirit stove and curling-tongs, Poirot reconstructs the charred note, revealing the words 'member little Daisy Armstrong.' He realizes Ratchett is actually Cassetti, the mastermind behind the Armstrong kidnapping case. Poirot explains the tragedy to M. Bouc and Dr. Constantine: the kidnapping, the ransom, the child's murder, the mother's death in childbirth, the father's suicide, and the nursemaid's suicide. This establishes the motive for multiple passengers.