On the seat opposite him was an American tourist. The pattern of his clothes, of his overcoat, the grip he carried, down to his hopeful friendliness and his naïve absorption in the scenery, even the guidebook in his hand, all gave him away and proclaimed him a small town American seeing Europe for the first time. In another minute or so, Poirot judged, he would break into speech. His wistful dog-like expression could not be mistaken.

The Labours of Hercules (1967)