Sherlock Holmes drew a long breath, and wiped the perspiration from his forehead. “I should have more faith,” he said; “I ought to know by this time that when a fact appears to be opposed to a long train of deductions, it invariably proves to be capable of bearing some other interpretation. Of the two pills in that box one was of the most deadly poison, and the other was entirely harmless. I ought to have known that before ever I saw the box at all.”

This last statement appeared to me to be so startling, that I could hardly believe that he was in his sober senses. There was the dead dog, however, to prove that his conjecture had been correct. It seemed to me that the mists in my own mind were gradually clearing away, and I began to have a dim, vague perception of the truth.

“All this seems strange to you,” continued Holmes, “because you failed at the beginning of the inquiry to grasp the importance of the single real clue which was presented to you. I had the good fortune to seize upon that, and everything which has occurred since then has served to confirm my original supposition, and, indeed, was the logical sequence of it. Hence things which have perplexed you and made the case more obscure, have served to enlighten me and to strengthen my conclusions. It is a mistake to confound strangeness with mystery. The most commonplace crime is often the most mysterious because it presents no new or special features from which deductions may be drawn. This murder would have been infinitely more difficult to unravel had the body of the victim been simply found lying in the roadway without any of those outré and sensational accompaniments which have rendered it remarkable. These strange details, far from making the case more difficult, have really had the effect of making it less so.”

Mr. Gregson, who had listened to this address with considerable impatience, could contain himself no longer. “Look here, Mr. Sherlock Holmes,” he said, “we are all ready to acknowledge that you are a smart man, and that you have your own methods of working. We want something more than mere theory and preaching now, though. It is a case of taking the man. I have made my case out, and it seems I was wrong. Young Charpentier could not have been engaged in this second affair. Lestrade went after his man, Stangerson, and it appears that he was wrong too. You have thrown out hints here, and hints there, and seem to know more than we do, but the time has come when we feel that we have a right to ask you straight how much you do know of the business. Can you name the man who did it?”

“I cannot help feeling that Gregson is right, sir,” remarked Lestrade. “We have both tried, and we have both failed. You have remarked more than once since I have been in the room that you had all the evidence which you require. Surely you will not withhold it any longer.”