Continuity mistake: Ralph Walton flubs the line and breaks character walking off set: he begins undoing his collar. He repeats the same action ('begins' to undo it) next time the camera is on him, and during a cut when he is in frame both shots, his hands jump off/on the collar. (00:04:35)
Continuity mistake: When the secretary leans in to console "Henry" after Walton has been escorted away, he pins her handkerchief hand to the desk; in the next shot the hand is turned differently and caught in midair. (00:07:45)
Continuity mistake: As Poirot, holding the family picture, turns around to ask Mrs. Oglander about the kids in the portrait, he suddenly has his finger near the middle of the frame, much higher than before. It keeps going up and down during the conversation. (00:36:40)
Answer: He definitely says "Belgian", but the subtitles get it wrong and show him saying "American."
Wblank71