pool and the discovery that more cattle had been driven away.

The information excited the cowboys greatly, and emphatic were
their opinions of the daring of the thieves in making another raid
and within a few hours after the men pursuing them had set out.

"They probably were watching us all the time," asserted the owner
of the Three Stars.

"Probably," agreed Mr. Wilder. "But what have you boys been doing
since you learned of the raid? You could almost walk your ponies
from the pool to here in all this time."

Before any of them could reply, however, a long, low wail rang out.
Surprised, the men glanced at one another,

"That sounds like a coyote, but it ain't," asserted Pete.

Again the cry broke on the air and was repeated twice.

"Why, it's the very same sound we heard in the mountains!"
exclaimed Larry. And his companions confirmed him.

"The same cry you heard in the mountains?" repeated Mr. Wilder.

"Yes, sir," and in a few words the elder of the brothers related
their adventures.

"Then it's a signal," declared Pete. "You boys have been followed.
It's a mighty good thing we were camping here."

"Those cries came from the plains. Mebbe it's the thieves going
for more cattle," declared Sandy.

"We'll find out what it is. Everybody to horse!" commanded Mr.
Wilder. "Pete, three or four of you go with Horace and the Aldens
to get their ponies. We'll ride up and join you."

CHAPTER XIX

A TERRIBLE PLOT

Quickly the men ran to the woods where they had concealed their
ponies, unhobbled, saddled and mounted them, riding along till they
came to where Pete and the boys were.

"Which way shall we go?" inquired Sandy when all were In their
saddles. "That cry came from straight ahead of us on the plains,
according to my judgment."

Pete and the other cowboys agreed with him, and, trusting to their
sense of direction, the owner of the Half-Moon said:

"Then we'll ride due east. Spread out abreast. The more ground we
can cover the better."

"But don't get too far apart," interposed the rancher from the
Three Stars. "Keep close enough together so you can see the man on
your right."

Rapidly were these commands given, and within fifteen minutes after
the mysterious calls had startled them the twenty-three horsemen
were advancing over the prairie, eyes and ears alert for sound or
sight of the men who had uttered the signals, the two Eastern boys
and Horace riding between Mr. Wilder a