Poirot is packing for South America when a mud-caked stranger walks into his flat, writes the figure 4 on a sheet of paper, and dies. Christie assembled the book from twelve magazine stories during the worst year of her life — her mother dead, her marriage ending, her own eleven-day disappearance still to come — and turned Poirot loose against an international conspiracy rather than a country house. It is the strangest thing she wrote.