Poirot, M. Bouc, and Dr. Constantine take stock of the evidence. They’re faced with a “small, dark man,” a prime suspect, who seems to have vanished, as he can’t be hiding on the train. Poirot lays out the facts of the case, but he’s less inclined to take clues and information as fact than M. Bouc. The irrefutable fact is that Ratchett was stabbed twelve times early that morning. But Poirot notes that the stopped pocket watch doesn’t necessarily give the time of the murder, as it could have easily been faked.
Poirot diagrams the case in his particular careful way, and it’s a way that has a healthy suspicion of convenient physical evidence. Poirot is suspicious of the stopped watch because it could be “faked,” and indeed, there’s no way to determine whether the crime scene was arranged by the murderer to mislead investigators.
The credibility of the witnesses is also a concern. Poirot uses the example of Mr. Hardman who first pointed them towards a small, dark man as a possible assailant. He notes that he can’t investigate the “bona fides” of each witness and can go only on “deduction.” He describes a process where each piece of information must be cross-referenced between the passengers. In Hardman’s case, his story of the small, dark man is corroborated by an “unlikely” source: Hildegarde the German maid.
Poirot cautions that the progress of this case is slightly unusual because it can’t involve the sort of rote policework that would reveal a witness as untrustworthy and, in turn, make for a boring mystery. Instead, each witness’s testimony must be balanced against that of others, seeking points of corroboration and disagreement, a task uniquely suited to Poirot’s “psychological” focus. In the case of the small, dark man, the fact that Hardman and Hildegarde can’t have known each other may suggest that each of them are telling the truth.
Poirot continues, focusing on the still unknown identity of the small, dark man in the conductor’s uniform. The man’s existence is directly or indirectly confirmed by the testimony of four witnesses, MacQueen and Arbuthnot in addition to Hildegarde and Hardman. But supposing he exists, Poirot says, he would have to be either hidden undiscovered on the train, which has been extensively searched, or disguised as one of the known passengers so completely that Ratchett wouldn’t recognize him.
Nevertheless, Poirot is skeptical, faced with two seeming impossible possibilities. According to both M. Bouc and Pierre Michel, no one could be currently on the train without their knowledge. On the other hand, as Poirot has noted before, no one on the train fits the description of the “small, dark man” and it’s unlikely that someone could be so completely disguised as to transform into one.
The same question attaches to the woman in the scarlet kimono. Seemingly, they’re confronted with a missing scarlet kimono and a missing conductor’s uniform, one lacking the button that Mrs. Hubbard found in her cabin. To that end, Poirot resolves to search each passenger’s luggage. He makes a grandiose prediction that the kimono will be found in one of the male passengers’ luggage and the conductor’s uniform in Hildegarde Schmidt’s luggage. As they’re wrapping up, Mrs. Hubbard bursts in screaming about a bloody knife in her “sponge-bag” and promptly faints.
Much of the information necessary to solve the crime hasn’t been found yet. Although Poirot isn’t certain that the small, dark man exists, an extra conductor’s uniform definitely does because of the button Mrs. Hubbard found. Further, Poirot himself saw a woman in a scarlet kimono, so that garment must be somewhere on the train.