He might have thought he was mistaken but for the marks of many feet around the base of the turret. The grass had recently been trampled down, especially on the inland side. Could there be another entrance, concealed by the ivy? He pulled the strong tendrils aside, and more birds came twittering out; but there was no sign of a second door. Somewhat perplexed, Jack raised his eyes and scanned the brickwork above, which the ivy had not yet reached. There was the wooden trap-door, let in the floor of the turret chamber, and a foot or two of rusty chain hanging down. "That must have been part of old Congleton’s machinery for hoisting his stores," thought Jack. "I wonder if the trap-door is fastened." It was quite clear that it opened inward, for there was no sign of a bolt outside. When the room was last used a bolt inside might have been slipped. If not, the trap-door could be opened from below. But how could it be reached? Only by a ladder, apparently. Was there a ladder hidden somewhere among the trees? He saw no other means of gaining the summit, for while the ivy was strong enough to bear his weight for a good many feet up, the brickwork above was smooth, in spite of the weathering it had undergone, and offered no grip for hands or feet. "I must look for that ladder," he thought. But after spending at least half an hour in searching the surrounding thicket he almost gave up the problem in despair. There was no sign of a ladder, and he had searched so carefully that one of the requisite length could not have escaped his eyes, however well hidden. What could he do? He did not like the idea of being beaten; especially as he had already failed once in his contest with the smugglers. Just then there seemed nothing for it but to go back to the boat, and perhaps bring a number of handy men from the cutter to break open the doorway. But before doing that he would have one more look. He returned to the tower. The mist was clearing somewhat. Once more he scanned each face of the tower in turn. And now he noticed, on the inland side, what had escaped him before. On the brickwork between the ivy and the chamber there were a number of small apertures dotted about, forming a kind of pattern—a spiral. The holes could not have come by accident, for they appeared to be at equal distances apart. He counted ten on the bare portion of the brickwork, and, looking intently, believed he caught sight of one more where the screen of ivy thinned off. His curiosity was now thoroughly awakened. What was the meaning of these holes? Were there more, concealed beneath the ivy? He pulled the strands of the plant aside, and with eye and hand examined the wall. There were no more holes, but what was this? He grasped an iron staple firmly imbedded in the brickwork; and three feet above, surely that was another! "Oho, my hearties!" he thought; "have I got you at last?"