The Big Four: The Original 12 Stories

When private investigator Hercule Poirot and his assistant Hastings get an unexpected visitor, they are propelled into the world of international intrigue.
The stranger who shows up in Poirot's doorway collapses and repeats Poirot's name and address and the number four over and over. The man speaks about an international crime cartel called the Big Four and describes its four leaders. Then the man dies.
Poirot begins his investigation with the four leaders. One is a Chinese political mastermind named Li Chang Yen. The second is an American. The third is a Frenchwoman, and the fourth is known only as "the Destroyer."
However, in his investigation of these cases, Poirot will be risking not only his life but that of his twin brother, Achille.