Next up for interrogation is MacQueen, Ratchett's secretary.
Let's review the interesting points:
MacQueen is surprised when Poirot tells him that Ratchett was really Cassetti.
MacQueen reveals that his father was the District Attorney on the Armstrong case.
After dinner, MacQueen talked to the English lady and then hung out with Colonel Arbuthnot in his compartment, where they talked about "world politics and the Government of India and our own troubles with the financial situation and the Wall Street crisis" (2.2.30).
They talked until around 2 a.m.
Arbuthnot and MacQueen did get out of the train at one point on the Vincovi stop, but it was super cold outside, so they got back on board.
They left the train by the dining car, which was barred, but did not bar it on the way back in. Oops.
He says he saw the conductor pass once in the hallway after the Vincovi stop.
MacQueen also saw a woman in scarlet headed toward the toilet. She didn't go back that way, though.
He does not smoke a pipe.
MacQueen is usually in the first class compartments with Ratchett, but they were all booked on this journey, so that's why he was in second class.