“Just what I mean,” nodded Colonel Haywood. “You remember you told me that when you were camped in the dark, near the beginning of the canyon, you were startled to hear the thud of many horses’ hoofs; and looking out, saw a troop pass by, many of the animals being led by unknown riders.”

“Yes,” Frank went on, quickly, “and at the time, Bob and myself just kept quiet, and they never suspected we were anywhere near. You see, we couldn’t make sure at the time whether they were some cow punchers from a ranch, taking home some new stock, and making use of the canyon over Thunder Mountain as a short-cut to the country beyond; or the rustlers. And as we hadn’t lost any saddle band just then, we didn’t care to mix in.”

“As near as I can figure out, Frank, it was that night, or the one before, when the raid was made on that Cibiou Creek ranch. And the more I

think of it, the firmer grows my conviction that over beyond Thunder Mountain somewhere Mendoza has his hidden corral, in some lost valley none of us know anything about!”

“Just as you say, dad, the chances look that way,” Frank admitted. “And if Circle Ranch meets with a loss any of these fine mornings, that’s where we’ll have to look to recover our stock. It may come sooner than any of us think. And dad, even if it’s the X—bar—X, or the Arrowhead, that stands the next loss, don’t you think we’d all better sink our differences, and unite against the common enemy?”

“I had made up my mind to that, Frank,” replied the stockman, firmly. “The time for our fall round-up is now close at hand, and the way things look we ought to make a good showing, unless something unforseen drops down on us. They say we have the finest herds in the whole section; and the branding before winter sets in ought to be the biggest ever.”

“Yes, and that’s just the reason we may be the next one to suffer at the hands of Mendoza,” observed Frank. “They say he keeps tabs on all the ranches, and even has many spies. In that way he knows about the condition of the herds, and makes his plans so carefully that he never was known to carry away anything but the very best.”

“What you say about spies has occurred to me more than once,” remarked the rancher. “I’ve even thought it possible that he might have one of his friends here. But it’s hard to suspect any of our boys, they’ve all seemed so faithful. In the other days, now, there was Spanish Joe, and his nephew, Abajo, both of whom I felt sure had communication with Mendoza. I was glad to be rid of the greasers. Still, there may be some one at Circle Ranch who sends word on the sly to the rustlers.”

“It would be a bad thing for him if the boys ever learned of his treachery,” declared Bob.

“Yes, they’d either tar and feather him,” said Frank grimly, “or else put it out of his power to send any more messages. But I hope it isn’t so, dad. Just now, with such fine prospects before us, and, as you say, the fall round-up at hand, we’ve got to be more watchful than usual over our herds, that’s all.”