The negro fell on his knees. "Oh, Gawd! Oh, Mr. Oakes! Dat is it. Dat is it. I never done any murder. No! no! _no!_" and he burst into racking sobs. The strain was terrible. Dowd opened a window. Hallen spoke. "How are you to prove his innocence, Mr. Oakes, as you said?" There was a slight element of doubt in the question. "Get up, boy," said Oakes; "get up." And turning to us, the cool man looked long at us all, then said: "The evidence showed conclusively that the weapon used was a heavy one, of 45-calibre probably--a revolver in all likelihood, and fired from a distance of about one hundred and fifty feet. That means a good shot. Now, this boy is right-handed, as you have noticed, but he could not use his right hand to shoot with, for the first two fingers have been amputated near the ends. Plenty of loss to preclude good pistol shooting! "To have used such a weapon with the left hand, and with such accuracy, is out of the question save for a fancy shot. If this boy could shoot like that, he would not be boot-blacking for a living. "Again, he has not noticeably strong arms, nor a wrist powerful enough to handle a heavy weapon properly. The boy is innocent--in my opinion." "Oakes, you are a demon," said Hallen. "Oh, no, I hope not; only I hate to see mistakes made too often. Poor devil!" And Oakes patted the boy on the back. With a pathetic, dog-like expression, sobbing with joy, the befriended negro seized the man's right hand and, kneeling, showered kisses upon it. _CHAPTER XVII_ _Checkmated_ The negro was led away. He was in better spirits now, and smiling as only a negro can. That extraordinary genius--the mystic Oakes--had, by a process of reasoning that Joe himself was able to follow, not only cleared him of suspicion, but made a _hero_ of him. The innate vanity of the race was reacting on the boy, and coming to the rescue of his nervous system, recently so severely strained. When he had gone, Oakes turned to us and, interrupting our exclamations, remarked: "Now that we are all here together, it would be wise perhaps briefly to review what clues we have obtained and their probable significance." We all assented to this suggestion, and by tacit consent Quintus Oakes began: "First, we have found that the _cartridge picked up_ in the cellar, and evidently dropped by the man in the robe, _is of the same pattern as the old ones in the pouch upstairs_. "They all belong to the old revolver which was taken away from its place--and for which another was substituted since my first visit here. With regard to its calibre (the important point), _that old revolver meets the requirements of our deductions about the weapon used to murder Mr. Mark_. Therefore we have a chain of evidence connecting my assailant in the cellar--the man in the robe--with the assassin.