“Of course!” he cried to himself. “Why didn’t I think of it before? Now to see if I’m right.” Boldly he stood up, in plain view of anyone from the window. The gun did not move to follow his action. It remained pointing in the same direction. “That’s it!” he exulted. “The gun is just fixed there! No one is holding it. It’s just like the trick once played in some battle. It’s a dummy gun. Hurray! I’m all right now. They have gone out, and left the gun pointing from the window to scare anyone who might come along.” Still Tom did not abandon all caution. He realized that though those guarding his chums might be gone from the top story, they still might be somewhere in the mill. “I’ve got to be careful,” our hero assured himself. “But I’ll take a few chances.” Approaching until he stood close under the open window from which the gun protruded, he tossed a stone up. It fell within the casement, and Tom heard it drop on the floor. “That ought to raise something,” he said, looking warily around to see if he was observed. There was no movement, and no one appeared. “Here goes for another,” said our hero. This time his stone hit the gun barrel, and it tinkled resoundingly. But it was not moved, proving conclusively that it was fastened there and not held by hands. “If I could only get Jack or some of the others to answer,” thought Tom. “I guess I’ll have to get inside and let ’em know I’m here. But how?” It was quite a puzzle. He knew he could not get to the third story from inside the mill, or at least he did not know the secret of the hidden staircase. “I haven’t time to hunt for a trick door,” he told himself. “I’ve got to find a way that’s plain to be seen. And I don’t want to go inside unless I have to, either, for if they are hiding and playing some trick they’ll nab me sure.” This thought made him look around apprehensively, and he decided to make a circuit of the mill from without, in order to make sure there was no one on the outside. He moved away from in front, and went to one side, the place where, on the plans, the secret staircase in the thick wall was shown to be. The ground sloped away on this side, and as Tom came opposite a pile of stones, he was startled and surprised to hear a voice saying: “Oh, if only Tom would come!” “Yes, I don’t see why he doesn’t,” another voice answered. “Maybe they have him, too,” spoke a third person. Tom stood as if electrified. “My chums!” he murmured. “Their voices! But where do the sounds come from?” He looked around to find the source of the hidden tones, but he could see nothing. CHAPTER XXIV THE SECRET ROOM Tom stared uncomprehendingly at the heap of stones. As he stood there he again heard the murmur of the hidden voices. Some one said: “I wonder how much longer we’ll have to stay here?” “Jack Fitch, as sure as I’m here!” gasped Tom. “Hang it all,” said a second voice, “I don’t see why Tom doesn’t do something.” “That’s Bert Wilson,” murmured our hero.