All around us are people, of all classes, of all nationalities, of all ages

M. Bouc speaks this quote, found in Chapter 3. The two men, sitting at lunch in the dining car, discuss the diverse community gathered on the train. This quote foreshadows the ending of the novel and acts as a very important clue in the case. When Poirot "sits back and thinks," he realizes that only in America could such a collection of people exist in one place. Knowing that Ratchett murdered Daisy Armstrong and that the murder was probably connected to the Armstrong family, an American family, this idea helps Poirot figure out the identities passengers on board the train. The quote provides foreshadowing not only because it is a major clue, but also because it reveals a possible relationship or origin of the passengers. This quote and conversation gets Poirot's imagination working, he begins to wonder how the passengers might possibly be linked. Poirot even suggests to M. Bouc that the passengers are linked because of something sinister, saying, "perhaps, all these here are linked together-by death." The quote also reveals the peculiar situation of the Armstrong family; they have come together for three days to seek revenge, will part in London and possibly not see each other again.