Oakes looked at him and smiled, then said: "Moore, where is your reasoning ability? Do you think, if the panel had been tampered with at the time the repairs were made, that the débris would have been left behind? No! It would have been removed with the rest of the dirt." We had gone to our rooms upstairs while the men were hunting through the tunnel to the well. They found nothing; everything was as we had left it after our adventures there. It seemed to us that, all things considered, the work on the panel must have been done by someone within the household, or, at least, that some of its members must have been involved in the matter. "It may have been accomplished at night, however, and by an outsider," said Oakes. "The servants' quarters are separate from the house. Anyone might easily have entered the cellar by the tunnel route. Still, there may have been collusion also." "It seems a nonsensical idea to leave the débris in the cellar," I said. "No, I think not," was the answer. "The care-takers are afraid even to enter that place. The miscreant knew that detection would be probable at the hands of strangers only." That evening Elliott and Martin left for New York. They were to bring the negro boy, Joe, to Mona. Late at night, before we retired, Oakes asked us to go with him into the parlor. "What for?" said I. "To forge another link in the chain--the strongest yet," he said. "What?" "Do you remember the cartridge I found in the cellar?" "Yes, yes; but you did not pay much attention to it, I thought." He looked gravely at me. "Stone, that cartridge probably corresponds in calibre to the one which was used in the murder of Mark." "Ah!" said Moore. "I had a notion of that myself. Why did you not tell us your opinion before?" "Because, when I found it, we were working on the Mansion affair only. I divined the value of the find; but why should I have mentioned it? I was not hunting the Mark murderer then." "Quintus, you consummate fox--you worked Hallen well!" "Not at all; business is business. What is the use of gossiping? There are no ladies to be entertained in _my_ profession, Doctor." He led the way to the parlor--we meekly following--to where a cluster of arms hung upon the wall: one of those ornaments of crossed swords, guns and a shield, so common in old houses. He remarked that he had noticed these arms on his previous visit. He looked at a revolver hanging across the shield, with a pouch beneath it, and then suddenly, in surprise, said: "Last time I was here, a few weeks ago, there was a large old-fashioned revolver here of 44 or 45 calibre. I remember it well, being interested in firearms. "This one now here is of a similar pattern and appearance, but of smaller calibre, and newer. Look! The cartridges in this pouch are of about 45 size; they belong to the old weapon and cannot be used with this one."