"I agraas wid ye, but s'pose it is a fire that yer fayther has started himsilf." Warren shook his head. "He would not do so imprudent a thing as that." "But he moight have in his eye that we'd be looking for something of the same." Still his friend was unconvinced. "He could not be certain that it would be noted by us, while he must have known that it was sure to attract the attention of the Sioux. No; I cannot be mistaken." "Do ye want to pass it by widout finding out its maaning?" "If it is father who has kindled the blaze, and he is looking for us, he will find some way of telling us more plainly----" "Do ye obsarve?" asked Tim, in some excitement. Beyond question the approach of the two young horsemen had produced an effect. The faint column of smoke which, until that moment, had climbed perpendicularly up the sky, now showed a wavy appearance, vibrating from side to side in graceful undulations, as though it were a ribbon swayed by human hands. But Warren, instead of accepting this as did his companion, regarded it as more indicative of danger. The Sioux that were responsible for the ascending vapor were aware of the approach of the couple, and were signalling the fact to others whose whereabouts was unknown to the whites. "Do ye moind," said Tim, "that two months since, whin we were hunting along the Big Cheyenne and got separated from him and Plummer, he let us know where they were in jist that way?" It was a fact. Precisely the same signal had been used by the parent to apprise his son and companion where he and Plummer were, though in that instance it was the employé who adopted the method. He was inclined for a few seconds to agree with his companion; but there was something in the prominence of the artifice, and the certainty that it would be noted by unfriendly eyes, that caused him to dismiss the belief. Enough doubt, however, had been injected into his mind to bring the desire for further investigation. "We will ride straight toward it, as though we intended to go to the camp or signal fire as it may be, but will turn aside before reaching the ridge, so as to avoid the trap that may be set for us. I had an experience yesterday afternoon something like that before you joined me." Strange it was that the couple, who, despite their youth, had learned so much of border life, forgot to keep watch of the rear, while giving so much attention to the front. Singular as it may seem, they had not looked behind them for the preceding half hour. The sight of the signal fire ahead so absorbed their interest that they neglected this obvious precaution; nor did it once occur to them that if the smoke was sent into the sky by hostiles, who meant it for the guidance of confederates, those same confederates were likely to be to the rear of them.