“Yes, yes; that was part of the game. As Richard Knighton his life was quite free from reproach. He was well born, well connected, did honourable service in the War, and seemed altogether above suspicion; but when I came to glean information about the mysterious Marquis, I found many points of similarity. Knighton spoke French like a Frenchman, he had been in America, France, and England at much the same time as the Marquis was operating. The Marquis was last heard of as engineering various jewel robberies in Switzerland, and it was in Switzerland that you had come across Major Knighton; and it was at precisely that time that the first rumours were going round of your being in treaty for the famous rubies.”

“But why murder?” murmured Van Aldin brokenly. “Surely a clever thief could have stolen the jewels without running his head into a noose.”

Poirot shook his head. “This is not the first murder that lies to the Marquis’s charge. He is a killer by instinct; he believes, too, in leaving no evidence behind him. Dead men and women tell no tales.