“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.
For, drawn in some such manner as are the water-marks in paper, visible only when held up to the light, so on the plan, there was marked out a secret staircase, leading from the second to the third floor of the old mill!
“By Jove!” cried Tom. “I have it. Now I see why that wall was so thick. The secret staircase is built in the thickness of the wall, and it doesn’t show from either inside or outside the mill. In fact it doesn’t show on the plans at first glance, and probably the old architect who drew them used a peculiar ink so that no one would know about the stairs. They must have been made so that anyone could get from the second to the third story of the mill in a hurry, and be hidden there when there was an attack by enemies. Well, I’ve made one discovery. Now to see how they use the stairs.”