Once he thought he heard the hoofbeats of the frightened beast, and doubled his speed from this encouragement. He was covering miles, and little by little the way was broadening in front till he knew he must soon emerge on the cold and dreaded desert to the north. The gaunt grey flanks of the distant impassable peaks were again visible above the right-hand crags, and ahead were the rocks and boulders of an open space which was clearly a foretaste of the dark and limitless plain. And once more those hoofbeats sounded in his ears, plainer than before, but this time giving terror instead of encouragement because he realised that they were not the frightened hoofbeats of his fleeing yak. The beats were ruthless and purposeful, and they were behind him.