"Again, some of them are missing; there were at least a dozen before, now there are only three or four. The old revolver and some cartridges have been taken away, and a newer weapon substituted." "Indeed! But why?" said Moore sceptically. "Partly because"--and Oakes was decisive, curt, master of the situation--"because this one cannot be loaded. See!" He then tried to turn the chamber and showed us that the mechanism was faulty. "The old revolver," said he in a low tone, "and some cartridges were taken away, and in order that its absence should be less noticeable, this one was left here--it being useless. "Now, boys, the cartridge I found downstairs on the cellar floor is a 45-calibre and belongs to those of the pouch and the original revolver, as you see." He took it from his pocket and showed us that it did _not_ fit the weapon in his hand but matched the cartridges in the pouch. It belonged to the _old_ weapon. "We are closing in," said I. "Yes--the man of the robe has the old revolver and cartridges; he took them within the last few days, finding his own weapon out of order. It is he who is responsible for the mystery in this house--and in all probability it is he who shot Winthrop Mark. You remember, the evidence at the inquest showed that a heavy revolver had been used--a 44 or 45 calibre--exactly such an one as the old weapon which I saw here." "Excellent, Oakes," remarked Moore. "There's only one objection." "Yes, I know," said Oakes. "You were going to ask why the fellow did not take all these cartridges and put his own in the pouch to match the weapon he left here." "Exactly," said Moore. "Well," said the detective, "he either had no cartridges of his own handy, or else, like all criminals, however smart, he tripped--the brain of no man is capable of adjusting his actions precisely in every detail." "Guess you're right. No man can be perfect in his reasoning, and, no matter how clever the criminal, he is almost certain to make an error sooner or later," said Moore. "Yes, but it takes peculiar power to discover it," I chirped. The events of the day had tired me, and my mind was growing confused. I desired to go to bed. Oakes smiled slightly. "No, Stone; it takes study, worry and patient reasoning to discover the faulty link in a clever criminal's logic--that is why there is a profession like mine." I was half asleep, but I heard him continue: "We may consider we have excellent cause to look for a man who has in his possession an ancient revolver and some very old dirty cartridges covered with verdigris, like these here." "Murder will out," I interpolated. "Yes, eventually, sometimes. However, it is easy to say, 'he who had that revolver did the murder,' but as it may have been destroyed since then, or thrown into the river, it is another thing to find the _man_." We were crestfallen. Oakes himself looked wearied. "I wish the whole Mansion was in the river, and there were a decent café round here," protested Moore.