"All around us are people, of all classes, of all nationalities, of all ages. For three days these people, these strangers to one another, are brought together. They sleep under one roof, they cannot get away from each other. At the end of three days they part, they go their several ways, never, perhaps, to see each other again" (37).
A theme throughout Christie's writing is the philosophical behavior of a number of characters throughout the story. The most important of which is M. Bouc when he notices the melting pot of ages, cultures, and statuses. This detail becomes one of the largest clues that Poirot uses in solving the case. As America is often known as the "the melting pot" of the world, this line from Poirot sets up a false atmosphere of chance and unpredictability when in truth, those on the train were perfectly orchestrated to be together.