"They do," said Smith, glancing impatiently at his watch. "Consult your memories of Dr. Fu-Manchu's habits--especially your memories of his pets." I reviewed in my mind the creatures gruesome and terrible which surrounded the Chinaman--the scorpions, the bacteria, the noxious things which were the weapons wherewith he visited death upon whomsoever opposed the establishment of a potential Yellow Empire. But no one of them could account for the imprints upon the dust of West's window-sill. "You puzzle me, Smith," I confessed. "There is much in this extraordinary case that puzzles me. I can think of nothing to account for the marks." "Have you thought of Fu-Manchu's marmoset?" asked Smith. "The monkey!" I cried. "They were the footprints of a small ape," my friend continued. "For a moment I was deceived as you were, and believed them to be the tracks of a large bird; but I have seen the footprints of apes before now, and a marmoset, though an American variety, I believe, is not unlike some of the apes of Burma." "I am still in the dark," I said. "It is pure hypothesis," continued Smith, "but here is the theory--in lieu of a better one it covers the facts. The marmoset--and it is contrary from the character of Fu-Manchu to keep any creature for mere amusement--is trained to perform certain duties. "You observed the waterspout running up beside the window; you observed the iron bar intended to prevent a window-cleaner from falling out? For an ape the climb from the court below to the sill above was a simple one. He carried a cord, probably attached to his body. He climbed on to the sill, over the bar, and climbed down again. By means of this cord a rope was pulled up over the bar, by means of the rope one of those ladders of silk and bamboo. One of the Doctor's servants ascended--probably to ascertain if the hashish had acted successfully. That was the yellow dream-face which West saw bending over him. Then followed the Doctor, and to his giant will the drugged brain of West was a pliant instrument which he bent to his own ends. The court would be deserted at that hour of the night, and, in any event, directly after the ascent the ladder probably was pulled up, only to be lowered again when West had revealed the secret of his own safe and Fu-Manchu had secured the plans. The reclosing of the safe and the removing of the hashish tabloids, leaving no clew beyond the delirious ravings of a drug slave--for so anyone unacquainted with the East must have construed West's story--is particularly characteristic. His own tabloids were returned, of course. The sparing of his life alone is a refinement of art which points to a past master." "Karamaneh was the decoy again?" I said shortly.