"I believe you are the one man in London who can help me," he continued. "I refer to a matter especially relating to your own particular study. I need hardly say that whatever you do will not be unrewarded." "That is neither here nor there," I said; "but before you go any further, allow me to ask one question. Do you want me to leave London at present?" He raised his eyebrows in dismay. "I certainly do," he answered. "Very well; pray proceed with your story." He looked at me with anxiety. "In the first place," he began, "I must tell you that I am chairman of the Lytton Vale Railway Company in Wales, and that it is on an important matter connected with our line that I have come to consult you. When I explain to you the nature of the mystery, you will not wonder, I think, at my soliciting your aid." "I will give you my closest attention," I answered; and then I added, impelled to say the latter words by a certain expression on his face, "if I can see my way to assisting you I shall be ready to do so." "Pray accept my cordial thanks," he replied. "I have come up from my place at Felwyn to-day on purpose to consult you. It is in that neighbourhood that the affair has occurred. As it is essential that you should be in possession of the facts of the whole matter, I will go over things just as they happened." I bent forward and listened attentively. "This day fortnight," continued Mr. Bainbridge, "our quiet little village was horrified by the news that the signalman on duty at the mouth of the Felwyn Tunnel had been found dead under the most mysterious circumstances. The tunnel is at the end of a long cutting between Llanlys and Felwyn stations. It is about a mile long, and the signal-box is on the Felwyn side. The place is extremely lonely, being six miles from the village across the mountains. The name of the poor fellow who met his death in this mysterious fashion was David Pritchard. I have known him from a boy, and he was quite one of the steadiest and most trustworthy men on the line. On Tuesday evening he went on duty at six o'clock; on Wednesday morning the day-man who had come to relieve him was surprised not to find him in the box. It was just getting daylight, and the 6.30 local was coming down, so he pulled the signals and let her through. Then he went out, and, looking up the line towards the tunnel, saw Pritchard lying beside the line close to the mouth of the tunnel. Roberts, the day-man, ran up to him and found, to his horror, that he was quite dead. At first Roberts naturally supposed that he had been cut down by a train, as there was a wound at the back of the head; but he was not lying on the metals. Roberts ran back to the box and telegraphed through to Felwyn Station. The message was sent on to the village, and at half-past seven o'clock the police inspector came up to my house with the news. He and I, with the local doctor, went off at once to the tunnel. We found the dead man lying beside the metals a few yards away