e to miss him,
but two causes operated to prevent this summary course: Vose wished
first to learn the business of the intruder, and there was a single
possibility in a hundred that he was neither an Indian nor an enemy.

The latter doubt could be solved by challenging the prowler with a
threat to fire, if instant satisfaction was refused, while the firing
could be made so promptly that the stranger would have no chance of
whisking out of reach. Vose decided to wait until he got some idea of
the other's business.

He could still dimly discern the form, but it was so obscure that had
it not been moving about, he would not have been able to distinguish
it or make sure it was within his field of vision.

While studying the phantom, the lower part of the veil of moonlight on
the other side of the canyon was twitched up for a hundred feet.
Lingering thus a minute, it was twitched still higher; then a third
flirt snatched it out of the gorge. The shifting of the moon had left
the canyon shrouded in darkness as before.

Nothing could have attested more strikingly the marvelous stealth of
the intruder than the fact that not one of the horses was awakened by
him. The approach of the great Geronimo and several of his Apaches was
betrayed under somewhat similar circumstances by the neighing of a
horse that they awakened, apparently when making no noise at all.

This prowler was a shadow in a world of shadows. If Hercules detected
his presence, the man succeeded in soothing the fear of the hybrid.

"_Halt or I'll fire!_"

Vose Adams's voice was low, but in the tomb-like stillness a
thunderclap could not have been more distinct. The hail, however,
produced no response. The angered Vose drew his Winchester to a level,
with his finger on the trigger, but when he ran his eye along the
barrel, he failed to perceive any target. He lowered the muzzle a few
inches and peered over the top. Nothing was discernible.

"You're there somewhere and I'll find you!"

Instead of rising erect, the sentinel advanced in a crouching posture,
so that his head was no higher than if he were on his hands and
knees.

This clever strategy was thrown away. Within five seconds, he was at
the side of Hercules, prepared and expecting to grapple with his
enemy, who, to his exasperation, continued invisible. Vose did not
require to have the matter explained to him, for he understood it.
Upon being hailed, the intruder instead of throwing up his hands or