Continuity mistake: As the future victim scoffs saying "Must be a great solace to you" to the Tollivers, his hand goes from midair to the teacup between shots. (00:11:30)
Factual error: When Poirot leaves customs with Mademoiselle Lyall, one of the supposed Italians asks in that language "What's happening, what is this noise?", which does not make sense in context, especially with the officer just shrugging and showing him the card. (00:32:55)
Other mistake: The man in front of Poirot in the line to embark argues supposedly in Italian with the officer: he does it in broken Italian but trying to pronounce informal words (even an incredibly explicit and vulgar curse at the end!) with unnatural cadence and a very thick Spanish accent. (00:28:30)
Factual error: The mysterious venom used to perpetrate the murder comes according to the English coroner from a "Vilitilio Occius", said to be a horn viper. Nothing wrong with artistic liberties making up animal species, but the name itself appears to be pseudo-latin with no real meaning or any closeness to other snakes, so not a particularly believable one.
Answer: He definitely says "Belgian", but the subtitles get it wrong and show him saying "American."
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