The doctor's voice ceased, and instantly I clapped my eye to the hole. He had changed his position so that his black eyes now looked straight at the aperture. My heart was in my mouth, for at first I believed from his expression that he had detected the gleam of my eyeball. But if so, he probably mistook it for a bit of mica in the rock, and paid no further attention. Then his lips moved, and I put my ear again to the hole. He seemed to be replying to a question that the foreman had asked. "If they do," he said, "they will never guess the real secret." Thereupon he turned on his heel, kicked a bit of rock off the track, and strode away towards the entrance. The foreman paused long enough to turn out the electric lamp, and then followed the doctor. "Well," asked Hall, "what have you heard?" I told him everything. "It fully corroborates the evidence of my own eyes and ears," he remarked, "and we may count ourselves extremely lucky. It is not likely that Dr. Syx will be heard a second time proclaiming his deception with his own lips. It is plain that he was led to talk as he did to the foreman on account of the latter's having informed him of the sudden discharge of my men this morning. Their presence within ear-shot of our hiding-place during their conversation was, of course, pure accident, and so you can see how kind fortune has been to us. I expected to have to watch and listen and form deductions for a week, at least, before getting the information which five lucky minutes have placed in our hands." While he was speaking my companion busied himself in carefully plugging up the hole in the rock. When it was closed to his satisfaction he turned on the light in our tunnel. "Did you observe," he asked, "that there was a second tunnel?" "What do you say?" "When the light was on in there I saw the mouth of a smaller tunnel entering the main one behind the cars on the right. Did you notice it?" "Oh yes," I replied. "I did observe some kind of a dark hole there, but I paid no attention to it because I was so absorbed in the doctor." "Well," rejoined Hall, smiling, "it was worth considerably more than a glance. As a subject of thought I find it even more absorbing than Dr. Syx. Did you see the track in it?" "No," I had to acknowledge, "I did not notice that. But," I continued, a little piqued by his manner, "being a branch of the main tunnel, I don't see anything remarkable in its having a track also." "It was rather dim in that hole," said Hall, still smiling in a somewhat provoking way, "but the railroad track was there plain enough. And, whether you think it remarkable or not, I should like to lay you a wager that that track leads to a secret worth a dozen of the one we have just overheard." "My good friend," I retorted, still smarting a little, "I shall not presume to match my stupidity against your perspicacity. I haven't cat's eyes in the dark."