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