The keen ears of the Moqui caught the words, although they were almost spoken in whispers, and only intended for Bob. He nodded violently, and Frank somehow found himself wondering whether, after all, the shrewd Indian might not be wanting to deceive him. He may have conceived the idea that these two white boys were the enemies of the queer old professor; and for that reason would be careful how he betrayed the man who trusted him. "Listen, Moqui," said Frank, putting on a serious manner, so as to impress the other; "we are the friends of the little-old-man who has no hair on top of his head. We want to see him, talk with him! It means much good to him. He will be glad if you help us find him. Do you understand that?" The Indian's black eyes roved from one to the other of those bright young faces. Apparently he would be foolish to suspect even for a minute that the two lads could have any evil design in their minds. Still, the crafty look on his brown face grew more intense. "He has some good reason for refusing to accommodate us, I'm afraid," Bob said just then, as if he too had read the signs of that set countenance. "Why don't you answer me, Moqui?" Frank insisted, bent on knowing the worst. "We are on the way now to find the man who gave you this letter that talks. We have some good news for him. And you can help us if you will only tell in what part of the Grand Canyon Echo Cave lies." The Indian seemed to ponder. Evidently his mind worked slowly, when it tried to grapple with secrets. But one thing he knew, and this must be some solemn promise he had made the man of science, never under any conditions to betray his hiding-place to a living soul. "No can say; in canyon where picture rocks lie; that all," he finally declared, and Frank knew Indians well enough to feel sure that no torture could be painful enough to induce Havasupai to betray one he believed his friend, and whose magic talking paper he carried inside his shirt, to prove his good character. "That settles it, Bob, I'm afraid," he remarked to his chum, who had been listening eagerly to all that was being said. "You might try all sorts of terrible things and he wouldn't whisper a word, even if he believed all we told him." "That's tough," observed Bob; "but anyhow, we've got something out of it all, because we know now that the silly old professor must be hiding in one of those cliff caves, trying to read up the whole life history of the queer people who dug their homes out of the solid rock, tier after tier, away up the face of the cliffs." "True for you, Bob, and I'm glad to see how you take it. I had hoped the Moqui might make our job easier, as he could do, all right, if only he wanted to tell us a few things. But we're no worse off than we were before, in all things, and some better in a few."