We've got all of the evidence, but M. Bouc is super confused, and Poirot is puzzled, too.
Poirot decides to review the evidence with M. Bouc, arranging it with "order and method" (2.13.16).
Here's the rundown:
Fact 1: Ratchett died the night before from twelve stab wounds.
Fact 2: The time of the crime might possibly be 1:15 a.m., unless the evidence of the watch was faked and the crime was committed earlier or later.
If the crime was committed at 1:15 a.m., the murderer must still be on the train.
Can they trust Hardman's account of the "small dark man with a womanish voice"? (2.13.32). Yes, because his story can easily be disproved with a simple cable. It's probably true. He is, at least, who he says he is.
Corroboration of Hardman's story: Hildegard Schmidt saw such a man, and Mrs. Hubbard found that button.
A smaller fact: Arbuthnot and MacQueen both mention seeing a conductor pass by their compartments, but Pierre Michel was sitting down the whole time.
Four witnesses, then, corroborate the small, dark man theory.
So, where is this man? Poirot proposes that one of the passengers was disguised. But which one? The only person who could fit the uniform would be the valet (a small man) or a tall woman – remember the womanish voice.
Poirot tells M. Bouc about Constantine's medical exam (how some wounds happened later than others) and everyone's heads start to spin.
Poirot seems to think there may be a "very simple" answer (2.13.61). After all, where are the man in the uniform and the kimono woman?
Now it's time to search everyone's luggage. Poirot predicts that the scarlet kimono will be in one of the men's bags, and the conductor's uniform in Hildegarde Schmidt's bag – certainly, if she is innocent.
Mrs. Hubbard enters, says she found the blood-covered murder weapon in her bag, and proceeds to faint.