A ruthless international cartel seeks world domination... Framed in the doorway of Poirot`s bedroom stood an uninvited guest, coated from head to foot in dust. The man`s gaunt face stared for a moment, then he swayed & fell. Who was he? Was he suffering from shock or just exhaustion? Above all, what was the significance of the figure 4, scribbled over & over again on a sheet of paper? Poirot finds himself plunged into a world of international intrigue, risking his life to uncover the truth about ` Number Four`.