As they had done on many another occasion, the boys divided the night into watches, each taking turn and turn about in keeping awake.
It was a moonless night, though the stars were bright enough. After a warm day, the myriads of insects seemed to be unusually noisy, and kept up a chorus that was soothing, rather than irritating, to the senses of Dick Armstrong, as he sat with his back braced against the trunk of a small tree.
Roger was sound asleep alongside; and, sitting there, Dick could hear the constant cropping of the horses as they continued to make a supper from the grass that grew in the open spaces, and still preserved its sweetness, despite the lateness of the season.
Now and again some distant sound would cause him to raise his head to listen; it might be the weird howl of a prairie wolf, the strange cry of a coyote, a new animal to both boys; or the hoot of an owl perched in some dead tree, and signaling to its mate.
But the night wore on, without anything out of the ordinary occurring, and Dick even began to imagine that his fears must have been groundless. Still, he could not regret having taken precautions; for it paid to be on the safe side always.
Then he suddenly sat upright. His manner indicated that his quick ears had caught some sound, however trifling, that seemed out of the common, and therefore, under the circumstances, suspicious.
It was as if a stone had been dislodged somewhere up on the little ridge, and in rattling down the side, caused a small avalanche. Still, a roving animal might have been the cause.
Dick turned his eyes upward. The top of the ridge happened to be devoid of undergrowth, and was sharply outlined against the starry heavens. One of the greatest of the planets was just about to set, and hovered above the ridge, as if on the point of sending out the last flickering gleam before dropping from sight.
Even as the boy sat there and looked, he saw something pass before this bright star. It was erect, and on two feet, therefore not an animal; moreover, Dick had seen the flutter of feathers crowning the scalp-lock, and he knew that it must be an Indian brave.