anded Professor Zepplin sharply. "Something wrong at
the camp?"

"My men think so. They say they hear shooting off in that direction, and
want to know if they shall ride out."

"You think it is a--a----" began Tad.

"A stampede? Yes; I should not be surprised."

"We must go," announced the lad, rising promptly.

"Why go?" asked Margaret.

"We may be needed."

"But my men have started already," replied the rancher. "They surely
will be help enough."

"Mr. Stallings will expect us. We may be able to be of some assistance."

"Well, if you must. Yes; you are right. Business is business, even when
one is out on a pleasure trip. It's a good sign in a young man. Tell
your foreman that he may call upon us to any extent."

"Thank you, I will," replied Tad.

Bidding their hosts a hasty good night, and promising to be on hand at
the appointed hour on the following day if the condition of the herd
permitted, the Pony Rider Boys ran for their ponies. In a few moments
they were racing toward camp. They, too, were now able to hear the
short, spiteful bark of the six-shooters.

It was a significant sound. They had heard it too many times before not
to understand it. In their minds they could see the hardy cowboys riding
in front of the unreasoning animals, shooting into the ground in front
of them, seeking to check the rush.

"What do you think about this business?" asked Tad Butler, drawing up
beside Ned Rector.

"I think there is more in this spook story than Colonel McClure knows
of, or, at least, will admit."

"So do I," answered Tad.

"We'll know when we hear how it happened."

Tad remembered, at that moment, the hasty departure of Ruth Brayton.

"I wonder--I wonder," muttered the boy to himself.

CHAPTER XXI

A CALL FOR HELP

"I told you so."

"You have told me so many things, Big-foot, that I can't remember them
all," laughed Tad. "What is it this time?"

"Trouble."

"Oh, you mean the stampede last night?"

"Yes."

"Tell me about it. You know I was not here when it started."

After a hard night's work, in which the Pony Rider Boys had toiled
heroically, the cattle once more had been rounded up and Big-foot and
Tad Butler were riding into camp for breakfast. It was the first
opportunity they had found to talk over the incident.

"Not much to tell. It happened so quick----"

"What time?" interrupted Tad.

"'Bout half-past nine, I reckon."

"Half-past nine," muttered the lad though