"What's the row?" asked the other, in somewhat the same guarded tone, as he managed to double over, and bring his face close to that of his friend.

"Charley Moi has just told me something," Bob went on. "You know we found out before now that he's got the greatest pair of ears ever for hearing things? Well, he says there's something or some one following us up this old crack!"

"Whew! that's nice, now. A regular procession, it seems," remarked Frank.

"Who d'ye think it can be; and would a bear or a mountain lion pick up our tracks this way?" continued Bob, who was trying to work his rifle around, so as to cover the rear.

"Wait! Let's all listen, after I send the word along to Hank and Chesty," remarked Frank.

When this had been done even the old cowman thought well enough of the idea to wait until they could find out the nature of the sounds that had reached the keen hearing of the wide-awake Chinaman.

It was only half light in the break of the rock, and the pa.s.sage they had been following thus far was so very crooked that no one could see more than twenty feet down the trail.

Still every eye was fastened on that point where the advancing man or animal would first appear. Frank, too, had his rifle bearing on the spot; and taken as a whole the appearance of the little company, flattened out against the break in the mighty rock wall, was rather threatening.

All of them could catch the sounds below now. Whoever came up the rock ladder must be unused to negotiating such a stairway, for they rattled small bits of loose shale down at times; and Frank felt sure he could hear a panting sound, very much like that which tired Bob had been making a minute ago.

And, as he listened, Frank made a discovery that caused him to tighten his grip on that reliable repeating rifle. There were two of the pursuers! And he antic.i.p.ated that the leader must come in sight ere another dozen seconds pa.s.sed!

There was some sort of movement now, down in the region of the little twist where the steep stairway of the old cliff dwellers made a turn.

Then a head and shoulders came into view.

Frank chuckled aloud. Just in almost that last second of time he had suddenly guessed the truth, when, in this clinging figure that was staring upward, as though filled with genuine surprise, he recognized an old friend.

It was Mr. Stanwix, the sheriff of the county!

He and his mate from the adjoining division of Coconino must have just had a glimpse of Charley Moi disappearing in the dark hole at the base of the cliff; and, being in pursuit of two shrewd law breakers, who had been known to appear in other dress than that of cowmen, perhaps the officers had concluded that here was something that ought to be investigated.

Frank immediately made a friendly gesture with one hand. He did not want to risk the chances of being fired upon by the officers of the law, who might take the little party for bad men. Then he beckoned in a fashion that the sheriff must readily understand to mean caution, and silence.

They saw Mr. Stanwix bend down as though he might be explaining to his fellow officer what an astonishing thing had happened. After that he came on, climbing the steep rock ladder as an exhausted person might.

Yet his nature was like that of the bulldog; and once he had started to do a thing, nothing could make him stop.

When he arrived at a point where he could make his way alongside Frank, squeezing past Charley Moi and Bob, the sheriff of Yavapai County turned an inquiring look upon his young friend.

Whereupon Frank started in to tell him just who the other three in the party happened to be; and that they were bent upon foiling the lawless game of three rascals plotting for a big stake.

In return Mr. Stanwix intimated that they had suspected something wrong when they saw from a little distance two persons, and one of them a Chinaman, disappearing in a cleft of the rocks. Further explanations must await a better opportunity, however. They were now too near the series of chambers connecting with one another to hesitate longer.

Besides, who could say what might not be going on up there a little further, in those holes in the wall where, ages ago, the singular people whom Professor Oswald loved to study about, had their homes, and lived on from year to year?

Old Hank, when he once more started upward, seemed to have become much more cautious. Frank could easily guess the reason. There was a strong possibility that the three schemers might have learned of their presence in the vicinity ere now. And of course Eugene knew full well why Frank and Bob had come to the Grand Canyon from their ranch home.

Suspecting that sooner or later the two boys might discover the way up to the cliff house, they would be apt to lay a trap of some sort, thinking to catch them napping when they ascended.

Old Hank could not be taken unawares any easier than might the wary weasel that has never been seen asleep by mortal eyes.

Frank, keeping well up by the heels of the little cowboy's boots, was ready to draw himself upward at the first sign of trouble. He knew when Hank had reached the top of the singular stairway fashioned by Nature for the benefit of those who built their habitations near the top of the cliff, far beyond the reach of enemies in the valley below.

A few seconds of suspense followed, while Chesty was following the veteran into the first hollowed-out apartment. Nothing followed where Frank had been expecting all manner of evil things.

"Perhaps they're asleep," was the new thought that flashed through his brain. He did not know what manner of man Uncle Felix was.

Now they were all gathered there in that outer chamber that might be called an ante-room of the various apartments running along the face of the cliff for some distance.

Even Charley Moi was there, full of curiosity, and willing to lend a hand after a fashion. Bob looked around; just as his chum had done as soon as he entered. He saw that some one had certainly been there recently. There were plenty of evidences to that effect.

Old Hank raised his hand with the forefinger elevated. It was recognized as a signal for absolute silence by all the others. Even Bob restrained his desire to ask questions; and every one listened, as if expecting to catch sounds.

Was that a human voice?

Frank started a trifle as the idea came to him. Still, it might only have been an additionally strong movement of the breeze; turning some angle that caused it to give forth a sound.

He turned to see if any of the others had heard, and judged from the way old Hank had his head raised that he, too, had caught the sound; also that it appealed to him as full of significance.

Again the veteran waved his hand. This time it meant not only caution, but an invitation to advance. Hank was about to pa.s.s into the next apartment, and wished the others to keep close at his heels.

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 doc.u.ment 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 a.s.sistance 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."

"Very well," replied the other, quickly. "Here's the situation then, in a nutsh.e.l.l. You suddenly appear before me, with a couple of men you claim are guides, but whom I have every reason to believe are low minions who are simply in your pay."