eye. But just wait till the right time comes, and see what you get then for doing this."

"Oh! well, suit yourself," returned Bob, with a laugh. "If the little brown-faced girl hadn't vamoosed I declare if I wouldn't feel like making you get down on your knees, and asking her to excuse you. Bah! you're not worth bothering about, Peg. Get out!"

The other moved away. He did not like the manner in which Bob said this; and he seemed to be afraid that perhaps the other might yet decide to press some further indignity on him.

When, however, he had reached the door of the inn, so that he could have a way of escape open to him in case of need, he stopped and shook his fist threateningly toward the saddle boys.

"You're both going to pay dear for this little fun, hear that?" he called, his voice trembling with passion. "I'll find a way to get even, see if I don't! And when Peg Grant says that he means it, too! Just you wait till I——"

And then, as Bob started to advance toward the hostelery Peg retreated in a panic, slamming the door after him.

"Well, what d'ye think of that?" asked Frank, who had been an amused observer of this curious scene.

"He's turned out just what I thought he would," remarked Bob, as he once more gained the side of his comrade, a grim smile on his face. "Whenever you run across a fellow who likes to boast of the way he does things, make up your mind he's a rank coward, every time. No matter what he claims he will do, there's a yellow streak in him somewhere, and sooner or later it's bound to show."

"I believe you're just about right, Bob," said Frank; "and it agrees with my own opinion exactly. Still, that fellow can be dangerous if he wants."

"So can a rattlesnake; but at any rate the reptile is honest, for he gives plenty of warning before he tries to strike; and that's more'n Peg would do, if I read him straight."

"You must keep an eye out for him after this, Bob. He'll never forgive you that crack. My! but didn't it drop him, though! Just like a steer would go down when the loop of a lariat closes on his foreleg. That fellow will lie awake nights trying to get even with you."

"Let him," remarked Bob, carelessly; "next time perhaps I'll put a little more steam back of my fist, if he pushes me too hard. That's the way they treat cowards back where I was brought up; and they call anybody by that name who will put his hand in anger on girl or woman. But see here, Frank, is this little affair going to force us to change our plans?"

"Whew! I forgot all about that," said the other, with a whistle, and an uplifting of his eyebrows. "If we go poking around Thunder Mountain, and Peg is there, with a couple of the tough cowboys he has trailing after him most of the time, Spanish Joe and Nick Jennings, perhaps we'll run up against a peck of trouble."

"Well, how about it?" asked Bob, with a shade of annoyance on his face.

"What do you say?" asked Frank, in turn.

"Go, by all means," came the quick response. "You don't think so mean of me as to believe I'd be frightened off by the bare chance of running across that fellow's trail out there; do you, Frank?"

"All right, call it a bargain, then. I'm with you through thick and thin, Bob. Let Peg have a care how he meddles with us. We're going to pay attention to our own business, and he'd better do the same. But what became of the little Mex? I thought I'd seen her face before, somewhere, but she skipped out before I could take a second look. Some cowboy, or cattle rustler's child from beyond the Rio Grande, I reckon. Well, come along, let's get in the saddle again, and finish our shopping. Then we'll go out to the country along the river, and put in a day waiting for Peg to have his chance at finding out what makes Thunder Mountain groan and shake just so often, and scare the Injuns out of their seven senses."

As the two chums swung themselves into their saddles, and cantered away, a head was thrust cautiously out from behind a pile of boxes near by; and then, finding the coast clear, the small girl who had been the cause of all the trouble darted across the courtyard, vanishing beyond the gate.

Frank and Bob went about making their purchases, first fastening their horses to a rail in front of the general store, where everything they needed could be bought.

More than one cattleman in passing would cast an envious eye toward those two splendid mounts, for they could not fail to catch the attention of anyone accustomed to judging horseflesh, as these Western men were. Still, it would be a bold man indeed, white or Indian, who would dare attempt to steal a horse in broad daylight, in a country where such a thief was treated to a rope when caught.

Frank had had considerable experience in roughing it, while his comrade was, in a measure, new to such a life. Consequently it was Frank whose judgment was called into play when making a selection of the things that would be essential to their comfort when on this new campaign.

Many articles they could do without; but a blanket apiece was absolutely necessary, as was a frying pan and coffee pot, two cups, as many platters, as well as common knives, forks and spoons such as prospectors and cattlemen use.

For food they took some bacon, coffee, dried meat, hard-tack in place of bread, a can of condensed milk, and several other things which would carry well.

"We must make them up in two packs," Frank went on; "so that each of us can fasten one to his horse, back of the saddle. And, as I'm an old hand at this business, just watch me get a hustle on. Next time you'll know how to go about it for yourself, Bob."

The Kentucky boy always studied everything his comrade showed him, for it was his ambition to excel in the many little tricks connected with the free life of the plains. Things were done so differently here from what he had been accustomed to in his old Kentucky home, before his father died, that they often puzzled him; but Bob was a persistent boy, and would never rest content until Frank could teach him no more.

Neither of them suspected what was going on outside, while they busied themselves in purchasing the supplies needed for the little campaign in the neighborhood of the mysterious mountain. And yet all was not as quiet as it might be.

The saddle boys had hardly been inside the general store ten minutes before a slinking figure might have been observed drawing nearer and nearer to the horses ranged along the bar. There were several besides the animals of our two young friends; but, somehow, the handsome black seemed to attract the entire attention of this shadowy form.

Twice he stopped, and assumed an attitude that would indicate his utter indifference to such commonplace things as horses. Then, finding that it must have been a false alarm, he would edge closer.

Finally he was beside the black horse, uttering low words such as cowboys make use of to soothe a restive steed when they mean to throw a saddle across his back, and cinch the girth.

Two men came out from the store, and drew near. The slim figure, finding it out of the question to flit hurriedly away, without attracting attention, which was just the thing he wished to avoid, commenced stroking the sleek side of the big black Kentucky thoroughbred, as though he might be a cowboy connected with the far famed Circle ranch of Frank's father.

Casting just one casual glance toward him, the men threw themselves into their saddles with the rapidity and grace of true plainsmen, and went galloping off.

Two minutes later the shadowy figure of the man flitted away from the line of horses that remained. If his purpose had been to steal the black he must have changed his mind, for there was no break in the chain of horses that stood there, impatiently scraping the ground with their forefeet.

A little later out came Frank and Bob, each bearing a compact bundle which they quickly fastened back of their saddles.

Bob was the first to mount, and this action was