How Does Your Garden Grow? - S3-E2
Other mistake: After Katrina is arrested, Mr. Delafointaine is reading about it on the newspaper. The newspaper is dated Thursday 23rd May 1935. The date is correct, the whole investigation does happen in a day, starting around 10 AM; Poirot is greeted by the couple with "Good afternoon" and to imagine that by the time he gets to their home Katrina's news (complete with picture of the arrest!) is already in a late edition of the newspaper (a local one, at that) is a bit too much of a stretch, with all the steps taken for the investigation, everything in broad daylight. (00:43:20)
Answer: He definitely says "Belgian", but the subtitles get it wrong and show him saying "American."
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