Bob was quivering all over with the fever of suspense, as well as pent-up eagerness. He did not know just how much longer he could hold in; for he wanted to yell. Still, he did not do it. Since coming to this wonderland country of the Southwest he had learned many lessons in the way of self control; and every day he was gaining more and more of a mastery over himself. Now Hank was in the second room, and still heading onward toward another hole in the wall, evidently the only means of communication between the various houses forming the little community. When he reached this, voices were plainly heard beyond. Hank kept right on, heading for yet a third doorway; and whoever was doing the talking, he or they must be in that further apartment; so that in another minute Frank expected to have his curiosity fully satisfied. CHAPTER XXI THE LITTLE OLD MAN OF ECHO CAVE "You admit you have carried the document with you, and that it's only a question of refusing to produce it, Professor?" Frank recognized that drawling voice. He had heard his father's cousin, Eugene Warringford, speak many times, and generally in this slow way. But Frank also knew that back of his apparently careless manner there was more or less venom. Eugene could hate, and hide his feelings in a masterly manner. He could smile, and then strike behind the back of the one with whom he was dealing. And somehow his very drawling voice always made Frank quiver with instinctive dislike. "I admit nothing, sir," came another voice, quick and nervous, yet with a firmness that told of considerable spirit. "You come upon me in my retreat without an invitation, and at first claim to be a warm admirer of my work, which you seem to have studied fairly well. But now you are taking the mask off, sir; and I can recognize the wolf under the sheep's clothing." Frank had heard that the old scientist, though a small man, was full of grit; and he could well believe it after hearing him speak. And Bob, who crouched close at the side of his chum, gave Frank a nudge as if to say: "What do you think of that for nerve; isn't he the limit, though?" Eugene laughed in his lazy way at being accused of evil intentions. Apparently he had about made up his mind that there was no use in longer beating about the bush. He had the old gentleman cooped up in this isolated place, where no assistance could possibly reach him. And backed up himself by a couple of reckless rascals, no doubt Eugene considered himself in a position to demand obedience. "Well, my dear old gentleman," he remarked, and by the sound Frank imagined the fellow must be lighting a fresh cigarette, for he seemed to puff between the words; "just as you say, what's the use of carrying the joke on any longer. Let's be brutally frank with each other from now on."