But Bob was not puzzling his head just now about what the symbols meant. He had had little difficulty in understanding that some one intended to warn them against the attacks of their old-time enemies. The question that gave both Bob and Sandy cause for speculation was the identity of the friend from whom these two birch-bark warnings came. It was not Blue Jacket, Bob knew. He had seen the young Shawanee brave draw similar figures, and they were slightly different from those now in front of him; even as one person's handwriting looks unlike that of another. And yet Bob felt positive that the work must have been done by an Indian. The mystery piqued his curiosity greatly. He and Sandy had tried to reason it out, and discover the identity of this unknown and unseen friend among the red men; but up to now they had not met with any success. After looking at the little strip of bark for a minute, Bob shook his head, as though once more compelled to abandon the solution of the puzzle; and, allowing it to roll up again of its own accord, he replaced the message in his pocket. "I'd give a lot to know who sent those two messages," he muttered, as he started to take the skin off the mink, not wishing to carry any more burden than seemed necessary, if they were to continue along the line of traps. "But, anyway, it's nice to feel that we've got a good friend among the Indians, who takes delight in upsetting the plans of those two precious rascals. Some day he may see fit to make himself known to us. But, I wonder what keeps Sandy. He surely ought to be here by now, for he had plenty of time to get to that trap, and fix it fresh, if it was sprung. I hope nothing has happened to him." He looked eagerly along the back trail, but failed to see any sign of the approaching figure of his younger brother. The afternoon was more than three-quarters past, and in another hour they could expect darkness to swoop down upon the land. Bob noted this fact when he again looked up toward the darkening heavens. "We will have to leave the rest of the traps until another day," he said to himself, uneasily. "I promised mother that I would not take any more chances than necessary, and she did not seem any too well satisfied about our crossing to-day, as it was. But, how queer Sandy does not come! Perhaps I'd better start back after him." Once this idea had taken root in his mind, Bob could not remain at ease. He arose to his feet, took the mink in one hand, with his rifle clutched in the other, and started off. Hardly had he taken ten steps when he heard a call. It was certainly his own name, and coupled with a word that sent a thrill through him. "Bob! oh! Bob! Help!" Instantly the boy dropped the mink, utterly unmindful of the value of the fine pelt. He started off at a swift pace, heading in the direction whence the shout came.