Poirot informs Hector MacQueen that his late boss was actually the criminal Cassetti. MacQueen reacts with surprise and anger, exclaiming “The damned skunk!” MacQueen reveals a personal connection the Armstrong case: his father was the district attorney who unsuccessfully prosecuted Cassetti. He even says that he’d have been willing to kill Ratchett himself, had he known, but he admits, “Seems I’m kind of incriminating myself.”
MacQueen’s response to the information that Ratchett was Cassetti diminishes suspicion in several ways. For one, his surprise seems authentic. Secondly, he openly admits that he’s personally connected to the Armstrong case. Finally, he even lets slip that he might have been willing to kill Ratchett. A guilty man might have tried to hide or downplay any of these facts.
MacQueen recounts his movements and activities on the previous night. He talked for a little bit with Mary Debenham, and then discussed world politics extensively with Colonel Arbuthnot until two in the morning. He generally finds “Britishers” uptight, but he liked the Colonel. MacQueen had left the train at Vincovci, but can’t remember if he barred the door to the platform on the way back in.
MacQueen corroborates the accounts of other witnesses. In the process, he reveals a prejudice against the British, but notes that Colonel Arbuthnot overcame it in his eyes, echoing the breaking down of barriers between the passengers that Poirot had previously observed. Poirot also tries to nail down whether an unknown suspect might have boarded the train, but MacQueen is unsure.