Ratchett becomes the symbol of pure evil in the novel. From the minute Poirot sees Ratchett in the hotel restaurant, he knows that he is a bad man. Poirot describes Ratchett as a "wild animal" and tells M. Bouc that when Ratchett passed "he could not rid himself of the evil that had passed me by very close." To the Armstrongs, Ratchett is evil as well. In the evidence gathering stage, when Poirot tells each of them about the crime and Ratchett's involvement, all of the passengers are outraged. The name Ratchett becomes synonymous with evil and terror. The close association of Ratchett and evil is purposeful, and Christie wants the reader to have no sympathy for this man.
Daisy Armstrong is symbolic of goodness and innocence. The three-year-old child, kidnapped and brutally murdered by an evil man for money, is the picture of purity. When each of the passengers speaks of the Armstrong case or specifically of Daisy, they can hardly contain their grief and anger that such a young, perfect life was taken. It is the duty of the Armstrong family to defend the good and murder evil, and it is their duty to defend Daisy and other young children like her by killing Ratchett.
Food is a symbol of society, sophistication and calm. M. Bouc, Dr. Constantine and Poirot always sit down at meals after every part of the investigation. Even after just having viewed Ratchett's dead, bloodied body, Constantine and Poirot go to the dining car and eat a full meal with M. Bouc. While eating his lunch, Poirot considers the case. When he is finished, he tells M. Bouc and Constantine that he knows Ratchett's true identity. Christie is careful never to leave out a meal, where and when Poirot is eating. In a time of great disorder and panic, food and the process of eating is ordered and sophisticated.