The scout, while he was thinking, was also keeping his eyes over the top of the kegs. Suddenly he detected a movement among the shadows that lay under the rocks of the island. Ceasing his reflections, he leaned across the kegs and watched intently. Somebody was doing something; but what? The shadows lay so thick about the island’s shore that he could not tell. Presently he saw a man moving out upon the surface of the treacherous quicksand. As the man walked, he seemed to be pushing something ahead of him. Curious, and profoundly interested, the scout kept his eyes on the dark figure. Farther and farther the man left the shore of the island behind him, still pushing a round object in advance of him as he walked. How was he able to keep on top of the bubbling sands? What sort of an object was it that he was pushing? The man appeared to be leaving a broad, dark trail behind him. For some time the scout was mystified. The man was laying a course that would bring him to the shore at the place where the kegs and boxes had been placed. When he had covered half the distance that separated him from the shore, the scout began to make discoveries. The long, round object the fellow was pushing in front of him had diminished by half since he had left the island shore. Plainly, then, he was leaving part of the object behind him; and it was equally plain that it was this object which gave him a secure foothold on the treacherous and shifting sands. The scout strained his eyes upon the diminishing roll in front of the figure. He made out long, thin slabs of wood, bound closely together by ropes. Ah! The scout had pierced the mystery. The thin slabs, bound together by ropes, when unrolled formed a sort of movable causeway, the length of each slab being sufficient to resist the soft sands and offer footing and support. By that time the man was quite near, and his bundle of slabs had been almost exhausted. The scout had made up his mind as to what he should do. Crouching down behind the kegs, he waited, every nerve tense as a forestay, and every muscle primed for quick action. CHAPTER XVIII. THE ISLAND. The actions of the man had they been planned by the scout himself, could not have worked out better for the scout’s plans. Tired from his work of unrolling the big bundle of slabs, the man stepped from the causeway and plumped down on one of the kegs, his back to the scout. The man was a stranger to the scout. He was one whom Buffalo Bill had never seen before. Quite likely he had helped Hendricks and Banks in carrying out the rascally plan for the abduction of Annie McGowan. While the man sat on the keg, Buffalo Bill rose softly behind him, caught him about the throat with both hands, and jerked him backward to the ground. The fellow’s surprise must have been overwhelming, but he had no way of manifesting it. The compression at his throat rendered any spoken sound impossible.