"I hadn't noticed it before," came the reply presently, "but, now that you call my attention to the fact, I really believe you are right. He does look as if something had gone wrong. I wonder what could have happened while we were away this afternoon." "We may have to take it out in guessing," Dick observed, "unless the Captain decides to tell us about it, which is hardly likely. But the rest of the men seem to be noisier and in better humor than usual. There's Andrew Waller keeping a lot of them roaring with laughter as he tells some comical story. I never saw him so lively, come to think of it." About the time all of them were through eating, Dick discovered that Captain Meriwether Lewis was walking directly toward the spot where he and his chum still sat. A couple of convenient stones had afforded them resting places; but, as the commander of the expedition paused beside them, both lads immediately sprang to their feet, courteously offering the captain a seat. "I will accept if one of you can sit tailor-fashion on the ground," remarked Captain Lewis, but without any sign of merriment in his voice, for he was still looking very grave. "I want to speak with both of you lads, and it is concerning a subject in which you are deeply interested." Of course that aroused their curiosity at once, and Roger lost no time in dropping upon the sand, where he could make himself fairly comfortable. As soon as they were all seated again the captain began: "While you two boys were away on your hunt this afternoon, something happened which deepened my suspicion that we have a traitor among us. By a mere accident I picked up a bit of paper that some one must have drawn from his pocket unknown to himself. Glancing idly at it I was startled at what I read." He looked around him as though to make certain that no eye watched his action, and then placed a small piece of paper, very much wrinkled and soiled, in Dick's hand. Together the boys fastened their eyes on the writing and made out the fragment of a sentence: "if you think it unsafe to stay longer in the camp, join us; but be sure and bring plenty of guns and ammunition along, for we need them." There was no signature, but the boys did not doubt in the least that the one whose hand had Penned this note of instructions was François Lascelles or his equally rascally son, Alexis. The question was, who could the recipient be, and how were they to find out. "After you found this paper, Captain, you watched to see if any one seemed to be searching for anything, I suppose?" Dick asked eagerly. "All the afternoon I have kept on the alert, but, whoever the villain is, he has either not discovered his loss, or else has assumed an appearance of indifference in order to blind hostile eyes." "But how do you suppose he could have received the message?" continued Dick.