All of a sudden the lad sat up wide awake.  He knew that he had heard something.  That something was a stealthy footstep.  The night was graying by this time, so that objects might be made out dimly.  Tad stood up, swinging his rifle into position for quick use.  For some moments he heard nothing further, then out of the bushes crept a shadowy figure.

“Chunky’s ghost,” was the thought that flashed into the mind of the young sentry.  “No, I declare, if it isn’t an Indian!”

It was an Indian, but the light was too dim to make anything out of the intruder.  The Indian was crouched low and as Tad observed was treading on his toes, choosing a place for each step with infinite care.  The watcher now understood why no moccasin tracks had been found about the camp, for he had no doubt that this fellow was the one who was responsible for all the mysterious occurrences in camp up to that time.

The Pony Rider boy did not move.  He wanted to see what the Indian was going to do.  Step by step the red man drew near to the canvas covered storage place, where they kept their supplies, arms, ammunition and the like.  Into this shack the Indian slipped.  Tad edged closer.

“I wonder what he’s after this time?” whispered the lad.  Tad thrilled with the thought that it had been left for him to solve the mystery.

His question was answered when, a few moments later, the silent figure of the Indian appeared creeping from the opening.  He had something in his hands.

“I actually believe the fellow is carrying away our extra rifles,” muttered the boy.

That was precisely what the redskin was doing.  After glancing cautiously about, he started away in the same careful manner.  Tad could have shot the man, but he would not do it, instead, he raised the rifle.

“Halt!” commanded the Pony Rider boy sharply.

For one startled instant the Indian stood poised as if for a spring.  Then he did spring.  Still gripping the rifles, he leaped across the opening and started away on fleet feet.  He was running straight toward where the ponies were tethered.

Tad fired a shot over the head of the fleeing man, then started in pursuit.  The Indian slashed the tether of Buckey, Stacy Brown’s mustang, and with a yell to startle the animal, leaped on its back and was off.

“That’s a game two can play at,” gritted the Pony Rider, freeing his own pony in the same way and springing to its back.

The shot and the yell had brought the camp out in a twinkling.  No one knew what had occurred, but the quick ears of the guide catching the pounding hoofs of the running mustangs, he knew that Tad was chasing someone.

“Everybody stay here and watch the camp!” he roared, running for his own pinto, which he mounted in the same way as had the Indian and Tad Butler.

Tad, in getting on Silver Face, had fumbled and dropped his rifle.  There was no time to stop to recover it if he expected to catch the fleeing Indian.  Under ordinary circumstances the boy knew that Silver Face was considerably faster than Buckey.  But pursuit was not so easy, though the Indian, for the present, could go in but one direction.