"I don't wonder at your feelings," I answered; "but now, see here, I want to make a most careful examination of everything. One of the theories is that Wynne crept down this rocky side and fractured Pritchard's skull. I believe such a feat to be impossible. On examining these rocks I see that a man might climb up the side of the tunnel as far as from eight to ten feet, utilising the sharp projections of rock for the purpose; but it would be out of the question for any man to come down the cutting. No; the only way Wynne could have approached Pritchard was by the line itself. But, after all, the real thing to discover is this," I continued: "what killed Davidson? Whatever caused his death is, beyond doubt, equally responsible for Pritchard's. I am now going into the tunnel." Inspector Henderson went in with me. The place struck damp and chill. The walls were covered with green, evil-smelling fungi, and through the brickwork the moisture was oozing and had trickled down in long lines to the ground. Before us was nothing but dense darkness. When we re-appeared the signalman was lighting the red lamp on the post, which stood about five feet from the ground just above the entrance to the tunnel. "Is there plenty of oil?" asked the Inspector. "Yes, sir, plenty," replied the man. "Is there anything more I can do for either of you gentlemen?" he asked, pausing, and evidently dying to be off. "Nothing," answered Henderson; "I will wish you good-evening." "Good-evening to you both," said the man. He made his way quickly up the path and was soon lost to sight. Henderson and I then returned to the signal-box. By this time it was nearly dark. "How many trains pass in the night?" I asked of the Inspector. "There's the 10.20 down express," he said, "it will pass here at about 10.40; then there's the 11.45 up, and then not another train till the 6.30 local to-morrow morning. We shan't have a very lively time," he added. I approached the fire and bent over it, holding out my hands to try and get some warmth into them. "It will take a good deal to persuade me to go down to the tunnel, whatever I may see there," said the man. "I don't think, Mr. Bell, I am a coward in any sense of the word, but there's something very uncanny about this place, right away from the rest of the world. I don't wonder one often hears of signalmen going mad in some of these lonely boxes. Have you any theory to account for these deaths, sir?" "None at present," I replied. "This second death puts the idea of Pritchard being murdered quite out of court," he continued. "I am sure of it," I answered.