The Big Four

Framed in the doorway of Poirot's bedroom stands an uninvited guest, coated from head to foot in dust. The man's gaunt face stares for a moment, then he sways and falls. Who is he? Is he suffering from shock or just exhaustion? Above all, what is the significance of the figure 4, scribbled over and 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'.