He stopped in a small restaurant and ordered a light meal. By the time he had finished this it was nearly dark, and he set out for his objective without further delay. He shortly reached the entrance to the alley, and, after casting a searching glance about him to make sure that he was unobserved, he slipped cautiously into the place. "It ought to be a lot easier for me to locate that trap door now than it was when I was here with Bart," he thought. "There's no ice now, and if there is a door, I'll be bound to find it." He proceeded cautiously up the alley, taking every precaution to avoid noise, and soon reached the blank wall that had so baffled him and his friends on a previous occasion. He drew a flashlight from his pocket, and when he thought he was close to the place where he and Bart had previously located the door he cautiously played the tiny spot of light over the ground. At first he thought he must be mistaken, as this part of the alley seemed to be like all the rest. But, looking closer, his heart leaped as he made out the outline of a heavy iron ring, lying flat in a recess in the pavement, and almost covered with gravel and dust. So cunningly was it concealed that it would inevitably have escaped observation unless one were actually looking for it. "There's a trap door here, all right," he exulted. "Now, I wonder if I can get in, or if it will be fastened from the inside. Here goes to find out." With the thought, he worked the iron ring loose from the dirt, set himself for the effort, and gave a tentative tug. The door did not give a particle, and he tried again, this time putting every ounce of his strength into the effort. The door gave a little, but with all his strength Frank could not lift it more than an inch or two. He tried again and again, but with no better result, and at last, to his great disappointment he was forced to give over the attempt for the time being. "Guess this is more than a one-man job," he thought to himself. "What I'll have to do is to bring Bart and Billy here to-morrow night, and I think the three of us can lift the door easily. I've made one big step, anyway, for now I know there is really a trap door here, and before we weren't sure of it." He pressed the iron ring down into its socket, scattered some earth and gravel over it, and at last satisfied that he had left everything as he had found it and in such a condition as not to arouse suspicion if the secret entrance was used by one of the plotters before he could return, he turned his footsteps toward camp. CHAPTER XV A BARE CHANCE Frank was now convinced that he and his comrades had really chanced on a big secret, and he was eager to get them and get to the heart of the matter. He was greatly disappointed that he had been unable to follow up the adventure that very evening, but with a soldier's philosophy promised himself better luck the next time, and swung off toward camp with a stride that soon brought him to his destination.