"Yes; the pair have hit the trail over the mountains. What are you going to do down here to-day?" "I am going down in the skip shaft." Jarvis nodded understandingly. "Mr. Penton said you might knock off and go with me." "Did he? That's fine. I'll see the mine captain and tell him." "I have told him already. You may come with me now, and we'll make a little examination on our own hook." Bob dropped his shovel, and, telling the shift boss where he was going, accompanied Steve down the ladder to the level below. There the lads looked over the platform by the tally-board, Steve pointing out where he was standing when he went through the floor. "I never knew there was a trap there," he said, pointing to the new planking that covered the hole through which he had dropped. "Nor I. I guess not many men in the mine knew about it. The timbers supporting it must have been rotten." "Perhaps," answered Steve dryly. "Come on up to the sub-level; we will begin our investigation there." Bob followed, though he did not fully understand the purpose of his companion. Rush made his way to the door on the sub-level through which the man Spooner had entered the shaft. The lad opened the door and stood peering in, holding his candle ahead of him as he did so. "You are not going in here, are you?" questioned Jarvis. "Yes." "Why not go in on the level below and save this climb?" "I have my reasons, old man. Do you see the red mud on the rungs of the ladder here?" "Yes, I see it; but what does that prove?" "No one has any business in this shaft and yet someone has been here rather recently, for the mud is still soft. That mud came from some one's rubber boots not so many moons ago." "You ought to be a detective," exclaimed Bob admiringly. "We will go down now. Be careful. This isn't a very safe place, and a misstep would take you to the surface by the route I followed two weeks ago." Once on the platform below, the boys halted. Holding their candles above their heads, they looked about them curiously. A new post had been set in place of the old one, the latter still lying on the platform. This the boys examined carefully. "You see, the post is in good condition, Bob. The post didn't give way, after all. I wonder how it was held up?" "Perhaps it rested on a piece of wood placed across these two posts that project up through the floor," suggested Bob. "Yes, that's so. I think you are right. But where is the piece? I should like to see it." Steve was hunting here and there with his customary energy, while Bob Jarvis stood looking on, not being quite sure what he should do. "You look about on that side, Bob. Be careful that you don't fall into the shaft. Here is sawdust on the floor, but I presume the men did that when they put in the new support. Hello! I've got something." Steve triumphantly held up a saw that he had found. "This may mean something and it may not. We shall find out when we get back again."