Chapter I. A Mysterious Visitor
 

"Boys! B-o-y-s!"

There was no response to the imperative summons.

Professor Zepplin sat up in his cot, listening intently. Something had awakened him suddenly, but just what he was unable to decide.

"Be quiet over there, young men," he admonished, adding in a lower tone, "I'm sure I heard some one moving about."

The camp of the Pony Rider Boys lay wrapped in darkness, the camp-fire having long since died out. Not a sound disturbed the stillness of the night save the soft murmurings of the foliage, stirred in a gentle breeze that was drifting in from the southwest.

The Professor climbed from his cot, and, without waiting to draw on his clothes, stepped outside. He stood listening in front of his tent for several minutes, but heard nothing of a disturbing nature.

"I believe those young rascals are up to some of their pranks--either that, or I have been having bad dreams. While I'm up I might as well make sure," he decided, tip-toeing to the tent occupied by Tad Butler and Walter Perkins.

Both were apparently sleeping soundly, while in an adjoining tent Ned Rector and Stacy Brown were breathing regularly, sleeping the sleep that naturally comes after a day in the saddle over the rugged, uneven slopes of the Ozark Mountains.

Professor Zepplin uttered something that sounded not unlike an Indian's grunt of disgust.

"Dreams!" he decided sharply. "I should not have eaten that pie last night. Pie doesn't seem to trouble those boys in the least, but it certainly has a bad effect on my digestive apparatus."

Having thus delivered himself of his opinion on the value of pie as a bedtime food, the scientist trotted back to his tent, his teeth chattering and shoulders shrugging, for the mountain air was chill and the Professor was clad only in his pajamas.

No sooner had he settled himself between his comforting blankets, however, than he suddenly started up again with a muttered exclamation.

"I knew it! I told you so!"

This time there could be no doubt. He plainly heard a dry twig snap near by; whether it were under the weight of man or beast, he did not know.

"There is something out there. It couldn't have been the pie after all. I'm going to find out what it is before I get back into this bed again," he decided firmly, slipping quietly from under the covers and peering out through the half closed flap of his tent.

As before, all was silence, the drowsy, indistinct voices of the night passing almost without notice.

But Professor Zepplin instead of waiting where he was, reached for his revolver and then strode boldly out into the open space in front of the tents, determined to solve the mystery, and, if possible, without waking the boys.

The reader no doubt already has recognized in the four boys sleeping in the little weather-beaten tents the same lads who some time before had started off for a vacation in the mountains where they hunted the cougar and the bobcat, the thrilling adventures met with on that journey having been related in a former volume entitled, "The Pony Rider Boys in the Rockies."

They will be remembered, too, as the lads who, in "The Pony Rider Boys in Texas," crossed the plains on a cattle drive, during the course of which Tad Butler bravely saved the life of the Chinese cook, by plunging into a swollen torrent; and later, saved a large part of the great herd, himself being nearly trampled to death in a wild stampede of the cattle.

It will be recalled also, how Tad Butler and his companions, after many strange and startling experiences, solved the veiled riddle of the plains and laid the ghost of the old church of San Miguel, for all time.

The stirring adventures of "The Pony Rider Boys in Montana," too, are still fresh in the minds of those who have followed the fortunes of the four lads since they first started out on their journeyings.

It will he recalled that in the latter story the lads experienced the thrill of being in a real battle between the cowboys and the sheep herders on the free-grass range of the north; how Tad Butler was captured by the Blackfeet Indians, and how, with the help of an Indian maiden, he managed to make his escape.

It will also be remembered that Tad was able to rescue another lad who, like himself, had been taken by the Blackfeet, and to return the boy to his father, none the worse for his exciting experiences. It will be recalled as well, how Tad Butler through his own efforts solved the mystery of the old Custer trail--a mystery that had perplexed and annoyed the ranchers along the historic trail for many months.

And now they were once more in the saddle, having chosen the Ozark Mountains in southwestern Missouri as the scene of their next explorations.

With them they carried a pack train of four mules, these being best adapted to packing the boys' belongings over the rugged mountains. For their guide they had engaged a full-blooded Shawnee Indian named Joe Hawk, known among his people as Eagle-eye, making a party of six, with eight head of stock in all.

At the time of the beginning of this narrative the Pony Riders were encamped on a fork of the White River some three days out from Springfield. Joe Hawk had asked permission to leave the party for the night to pay a visit to a fellow-tribesman who lived somewhere in the mountains to the west of them.

On second thought it occurred to Professor Zepplin that perhaps it might have been Joe, or Eagle-eye, as the boys had decided to call the Indian, whom he had heard skulking about the camp.

"Eagle-eye," he called softly.

There was no response, so the Professor, gripping his gun resolutely, crept along toward the opposite side of the camp where the noise had seemed to come from. So quietly had he moved that he made scarcely a sound, until suddenly there came a commotion that more than made up for the noise he had so successfully avoided before.

Stacy Brown, with his usual forgetfulness, had left his saddle in the middle of the camp. The Professor caught his toe on the obstruction, measuring his length on the ground instantly, where he floundered about for a few seconds.

"Instead of discovering the other fellow, I think I am discovering myself," he growled, scrambling to his feet, gingerly rubbing a knee.

Now the Professor walked with a distinct limp, while his bare feet seemed to pick up every sharp pebble in camp, all of which added to his discomfort.

"I'd make a nice sort of scout," he muttered. "Everybody within a mile of me would know I was coming even before I got started, I guess--"

The Professor suddenly cut short his words, and crouched down close to the ground. He thought he heard something ahead and a little to the right of him.

"Who's there?" he demanded.

No answer being made to his inquiry, he gripped his gun more firmly and crawled cautiously toward the spot where he thought he had heard some one moving. The night was so dark that he could make nothing out of the shadows about him, being obliged therefore to trust entirely to his sense of hearing.

Now he was certain that some one was in camp who had no business there, for the sound of footsteps was plainly borne to his ears--cautious, catlike steps, as if the intruder were seeking to get away without attracting attention.

The Professor, determined to capture the intruder, getting down on all fours to avoid possible detection, made a wide detour so as to come up behind where the fellow seemed to be at that moment. After much labor he managed to reach the desired position.

The Professor straightened up to listen. He must be close upon the other by this time. But what was his chagrin to hear those same footsteps on the opposite side of the camp. Professor Zepplin by much effort had just come from the other side himself.

"Stupid!" he muttered. "I'll take no roundabout way this time. I'll go straight ahead and be as quiet about it as I can."

He did so. He moved straight across the camp ground, not forgetting the saddle which he carefully avoided, but narrowly missing falling over it a second time.

By the time he had crossed to his former position, the intruder had done likewise. Professor Zepplin dodged behind a tree.

By this time the scientist was beginning to feel a little worried. He could not understand what the other fellow's object might be. If it were robbery, the fellow certainly would desire to get away as quickly as possible, rather than remain when he knew that efforts were being made to capture him. If not plunder, what could be his purpose?

With suddenly formed determination, Professor Zepplin strode out from his hiding place, starting for the other side on a run.

The other man did the same, and the only result of the move was that their positions were exchanged.

Once more the Professor decided to try strategy and see if he could not come up behind his opponent.

At the same moment the visitor apparently decided to resort to the same tactics. They went in opposite directions, however, to carry out their purpose, and when each arrived at the place it was to find that the other was opposite him again.

The Professor's bare feet were in a sad state by this time, his pajamas were torn and his hands were worn tender from using them for feet when running along on all fours. At the same time his temper was wearing to a point of dangerous thinness. It was likely to break down the slender barrier that held it at almost any time.

Suddenly he realized that the intruder had been silent for some minutes, and the Professor decided that it was time he ceased thinking over his own troubles and paid more attention to what the other man was doing.

"Now, I wonder what he is up to," growled the scientist. "I believe he has given me the slip and gotten away. Here I've been dreaming for minutes. I'll slip some myself and see if I can't surprise him if he's there yet."

Once again he started across the camp ground, without resorting to any of his former tactics, other than to proceed with extreme caution, covering the intervening space with long, careful strides.

Reaching the rock, he paused to listen, but could hear nothing.

Gun ready for instant use, Professor Zepplin dashed around the corner of the rock, running plump into the arms of the fellow whom he had been so successfully dodging for the past twenty minutes.

So startled was the scientist that he dropped his revolver, throwing both arms about his antagonist. He was surprised at the slenderness of the fellow, though he quickly discovered that what the other lacked in bulk he easily made up for by his lithe, supple body and muscular arms.

Almost before Professor Zepplin had collected his wits sufficiently to make any sort of defense he found himself lying flat on his back, with his opponent sitting on top of him, both wrists pinioned to the ground in an iron grip.

There seemed to the Professor something strangely familiar about the figure that was holding him down so firmly, but he did not try to analyze the impression. He had other things to think of at that moment.

"I'll wait a second until he lets up ever so little, then, with my superior weight, I ought to be able to throw him--"

"I've got you this time. What do you mean by prowling about our camp at this time of the--"

"Wha--what--who--who--" exclaimed the Professor.

"What!" fairly shouted the other. "Who--who are you?"

"I'm Professor Zepplin. Who are you?"

"Oh, shucks! I'm Tad Butler," answered the boy, hastily releasing his prisoner, and, more crestfallen than he would have cared to admit, assisting the Professor to his feet.

"What do you mean, you young rascal?" demanded the Professor, grasping the boy by the shoulders and shaking him vigorously. "I say, what do you mean by playing such pranks on me as this? Why, I might have shot you. I--"

"You are wrong, Professor; I have not intentionally played pranks on you--"

"Yes you have--yes you have," fumed the Professor.

"I might accuse you of doing the same thing to me, only I know you didn't get up in the middle of the night to play hide and seek with a boy--"

"Then what does this mean? Answer me instantly!"

"I can do so easily. The fact is, I heard somebody prowling around. The slight noise awakened me--"

"I should think it might," snarled Professor Zepplin.

"And, without waiting to dress, I slipped out--"

"And led me a nice chase. Look at me. There isn't a spot on my body that isn't black and blue. And to think I've been running around here in my bare feet trying to catch you--"

"You haven't entirely. You were chasing the same thing that I was," answered Tad thoughtfully.

"What's that? What's that you say?"

"I mean that somebody was here--somebody who had no business to be here."

"You mean--"

"Yes, I mean that after I had been out here a few moments I distinctly heard two men. One of them, it appears, was yourself. Who the other was I don't know. He evidently got away. As I couldn't follow both of them, I chose you. You seemed to be the easiest one to catch. I was right, wasn't I?" laughed the boy, at the thought of the game they had been playing with each other.

"Somebody else here? I knew it, I knew it," exclaimed the Professor. "When I first came out you were sound asleep. I must have awakened you when I fell over the saddle out there. Who left that thing there for me to nearly break my neck on?" he demanded angrily.

"I guess it must be Chunky's saddle."

"Of course. I'll talk to him in the morning. I'm going to bed. I'll catch my death of cold."