"It's my opinion that those hounds were poisoned," he declared.

"Poisoned!" exclaimed the boys.

"Yes. There's some mysterious work being done around this camp. I'm going to find out who is at the bottom of it; then you'll hear something drop that will be louder than a boulder falling off the rim of the Grand Canyon."

"This is a most remarkable state of affairs." said the Professor.

"Surely you do not suspect the man Chow?"

"No, I don't suspect him. It's someone else. I had a talk with Chief Tom. He told me some things that set me thinking."

"What was it?" asked Tad.

"I'm not going to say anything about it just now, but I am going to have this camp guarded after to-night. We'll see whether folks can come in here and play tag with us in this fashion without answering to Jim Nance."

"I'll bet the ghost has been here again," spoke up Stacy.

"Ghost nothing!" exploded Nance.

"That's what you said before, or words to that effect," answered the fat boy. "You found I was right, though. Yes, sir, there are spirits around these diggings. One of them carried away my gun."

"We will divide the night into watches after this. I am not going to be caught napping again," announced Nance.

That night the guide sat up all night. Nothing occurred to arouse his suspicion. Next day they went out lion hunting without dogs.

Nance got a shot at a cat, but missed him. The next day the Professor killed a cub that was hiding in a juniper tree. It was his first kill and put the Professor in high good humor. He explained all about it that night as they sat around the camp fire. Then the boys made him tell the story over again.

Nance took the first watch that night, remaining on duty until three in the morning, when he called Tad. The latter was wide awake on the instant, the mark of a good woodsman. Taking his rifle, he strolled out near the mustangs, where he sat down on a rock. Tad was shivering in the chill morning air, but after a time he overcame that. He grew drowsy after a half hour of waiting with nothing doing.

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 circ.u.mstances 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.

The spirited mustang on which Tad Butler was mounted, appearing to understand what was expected of him, swept on with the speed of the wind. Small branches cut the face of the Pony Rider like knife-blades as he split through a clump of junipers, then tore ahead, fairly sailing over logs, boulders and other obstructions.

The Pony Rider boy uttered a series of earsplitting yells. His object was to guide Jim Nance, who, he felt sure, would be not far behind him. The yells brought the guide straight as an arrow. Tad could plainly hear the foot beats of Buckey as the two riders tore down the Canyon, each at the imminent risk of his life.

"If he has a loaded gun, I'm a goner," groaned the lad. "But the ones he stole are empty, thank goodness! There he goes!"

The Indian had made a turn to the left into a smaller canyon. By this time the light was getting stronger. Tad was able to make out his man with more distinctness. The boy urged his pony forward with short, sharp yelps. The Indian was doing the same, but Tad was gaining on him every second. Now the boy uttered a perfect volley of shouts, hoping that Nance would understand when he got to the junction of the smaller canyon, that both pursued and pursuer had gone that way.

Nance not only understood, but he could hear Tad's yells up the canyon upon arriving at the junction.

"Stop or I'll shoot!" cried the boy.

The Indian turned and looked back. Then he urged Buckey on faster.

That one act convinced Tad that the redskin had no loaded rifle, else he would have used it at that moment.

With a yell of triumph the boy touched the pony with the rowels of his spurs. Silver Face shot ahead like a projectile. He was a tough little pony, and besides, his mettle was up. Now Tad gained foot by foot. He was almost up to the Indian, yelling like an Indian himself.

The redskin tried dodging tactics, hoping that Tad would shoot past him.

Tad did nothing of the sort. The boy was watching his man with keen but glowing eyes. The call of the wild was strong in Tad Butler at that moment.

Suddenly the boy drew alongside. Utterly regardless of the danger to himself, he did a most unexpected thing. Tad threw himself from his own racing pony, landing with crushing force on top of the Indian.

Of course the two men tumbled to the ground like a flash. Then followed a battle, the most desperate in which Tad ever had been engaged. The boy howled l.u.s.tily and fought like a cornered mountain lion. Of course his strength was as nothing compared with that of the Indian. All Tad could hope to do would be to keep the Indian engaged until help arrived.

Help did arrive within two minutes; help in the shape of Jim Nance, who, with the thought of his slain hounds rankling in his mind, was little better than a savage for the time being.

"Here!" shouted Tad. "Take him---hustle!"

Then young Butler drew back, for Nance, seeing things red before his eyes, was hardly capable of knowing friend from foe.

Whack! b.u.mp! buff!

How those big fists descended!

For three or four seconds only did the redskin make any defense. Then he cowered, stolidly, taking a punishment that he could not prevent.

"Don't kill the poor scoundrel, Dad!" yelled Tad, dancing about the pair.

But still Nance continued to hammer the now unresisting Indian.