midnight
He was the silent , impassive-faced stoic of his race . After darkness had set in the boys scanned the mountains for the light of a campfire , but there was no light to be seen . The Pony Rider Boys ' campfire , however , was blazing up brightly , they having built up a large fire on purpose to attract the attention of the men who had made the smoke signals from the low mountain peak , low in comparison with the ten and fifteen thousand feet ranges about them . The boys turned in at midnight , a late hour for them , and were sound asleep within two minutes thereafter . They were aroused an hour later by the most terrifying roar they had ever listened to . `` What 's the matter ? '' cried Tad , springing from his tent , trying to pierce the darkness with his gaze .