“I’ve had visitors!” cried Tom. “And two-legged ones at that! Someone has been here, running about!” Well might he say that, for the place was in confusion. The neatly-made-up cots had been pulled apart, the valises and suitcases, of himself and his chums, had been opened, the garments tossed about. Boxes and packages had been searched. “This is the work of that old hermit, or else Skeel and his two cronies,” decided Tom. “They must have known I’d go away from camp, and they watched their chance to sneak in. Oh! if I had only known it!” He looked about to see if anything had been taken, but there was no sign of anything missing, though it was hard to tell definitely because of the manner in which things were scattered about. “I wonder what they could have wanted?” asked Tom aloud, and, having no one to answer it, he replied to his own question. “It couldn’t have been me,” he resumed, “though they may have done this for spite because they didn’t catch me. No, that would hardly be it. They would have done worse damage if they had done it just because of anger. It was something else. They were searching for something. I have it! The plan I found! That’s what they want! Maybe, after all, it’s the original and not a copy, and they can’t go on with the search without it. That’s it, I’ll wager a cookie! I wonder if I have it safe?” From an inner pocket he took the piece of paper containing the map. “Here it is,” he murmured. “I’m glad I thought to take it with me, and not leave it around here. My! but they must be desperate to take such chances for this document. That shows how valuable it is.” Returning the paper to his pocket, Tom took an hour or so to straighten out his camp. Then, getting supper, which he ate in lonesome silence, he sat down by the fire to think. “I’d be glad even if we had a dog,” he mused. “The next time I go camping I’ll take one along. Now let’s see where we are at. “Dick, Jack and Bert are prisoners in the old mill. That’s my first fact. Second, I’ve got to rescue ’em. Third, is this plan going to be of any use to me?” Again he took it out to look at it, but the flickering of the campfire proved too uncertain, and he decided to go in the tent and examine it by the light of a lantern. “Maybe, now that we’re not so excited over it, I can make out things on it that I couldn’t before,” he told himself. But the first half-hour’s scrutiny did not develop anything. The plan appeared to be just that and nothing more. “And it’s here, in the third story, where the boys are held prisoners,” mused our hero, as he put his finger on that part of the drawing. “Only there’s no stairway shown, as far as I can see.” He looked closely at the plan, lifting it from the table and holding it between himself and the light. As he did so he made a most remarkable discovery. He fairly shouted as he saw it.