"Well, what do you know about that!" exclaimed Bud. "What do you reckon the professor is doing, or was doing, over there?" asked Nort. No one answered him, but Bud turned toward Old Billee. The veteran cow puncher had spoken of "suspicions." Bud wondered if they were along a line that might connect with the professor. But if Old Billee had anything to say he was keeping it to himself. Though there was a quizzical look on his face as he observed the approaching horseman, of whom Professor Wright appeared to form the nucleus. "If those fellows think they can cover up their game by getting one of our friends to accompany them, they've got another guess coming," said Bud grimly. "That's right--don't let 'em cross!" cried Dick. But the "spy," as he was called for want of a better name, and his Mexican companions, seemed to have no intentions of fording Spur Creek which, though rather wide, was not very deep in some places. Reining in their horses when yet several hundred feet from the southern bank of the stream, the Mexicans halted, and the one who had ridden up alone several days before, waved his hand toward the waiting cowboys, and then motioned to the professor as if saying: "There are your friends." As a matter of fact that is what he did say, for Professor Wright said so when, a little later, he had urged his horse across the creek, and had joined the boy ranchers and their friends. Watching the scientist cross the stream, the Mexicans stood for a moment, rather picturesque figures on the southern bank and then, when the "spy" had again lighted a cigaret, and waved his hand as if in mocking farewell, the band rode off. It was a very silent contingent from Diamond X that watched the lone approach of Professor Wright. The scientist seemed worn to weariness, and looked worried as he smiled at his acquaintances and said: "Well, here I am." "So we see," observed Billee Dobb, dryly, not to say sarcastically. "Where have you been?" asked Bud. "Did they capture you and hold you for ransom?" Nort wanted to know. "What happened?" asked Dick. "With my usual stupidity I became lost again," explained Professor Wright. "I have been out looking around, 'prospecting,' I believe it is called, seeking a new deposit of fossil bones. I wandered farther than I intended, and got across the creek. I found I was on the wrong trail, and that there was nothing much of interest there, so I turned to come back. But I must have turned the wrong way, and have gone south instead of north, for I began to note signs that I was approaching the Mexican border. "I started back then, when these gentlemen overtook me. They were very kind and when I told them where I wanted to go they agreed to accompany me." "Passing over for the time being the use of the word 'gentlemen,' and realizing that you probably don't know them as well as we do, I'd like to ask if they said why they were coming this way?" asked Billee.