"Oh, Del Pinzo and Hank Fisher had pull enough to get him out of jail, after he'd served only part of his term for infecting our stock," said Bud. He had reference to something which is explained in the volume immediately preceding this. Del Pinzo was a notorious Mexican half-breed who, more than once, had made trouble for the boy ranchers. Hank Fisher was the owner of Double Z ranch, adjoining that of Square M, one of Mr. Merkel's, and also adjoining Happy Valley. Pocut Pete was believed to be a tool of these two unscrupulous men, and Del Pinzo had at his command Several Greasers who slipped back and forth over the Mexican border, not far from which were located the holdings of Mr. Merkel and the boy ranchers. "Well, this is a stethoscope all right," went on Nort, as Bud turned toward his pony, with the evident intention of mounting. "And I'd give a lot to know what it's doing here, and who dropped it," spoke Bud. "Let's look around a little more. I'm not at all satisfied with this. I sure saw, some one here, and this proves it," and he stuffed the doctor's instrument into his pocket. "It doesn't prove that the man you saw--or thought you just saw--sneaking around here dropped it," spoke Nort. "We've been away for a week, and it may have been dropped any day within that time." "Yes," agreed Bud. "But who was monkeying around here as we rode back to camp? That's what I want to know!" However, search as the boy ranchers did, they found no midnight visitor. All was quiet at their camp, save for the distant howl of a coyote, and the splash of the water into the reservoir. All the stock had been driven away from Happy Valley to the big round-up at Diamond X, but soon the fertile glade would again be dotted with hungry cattle. "Well, I reckon we'll have to give up," said Bud, when a thorough search had been made, and no one discovered. "The tunnel door doesn't show any signs of an attempt having been made to bust it; does it?" asked Dick. "Not as far as I can see, in this light," Bud replied. "We'll take a stroll up here in the morning," he went on as he thrust the stethoscope into his pocket. "Now for a little grub, and then to hit the hay. Oh, boy! But I to tired!" So were the others, and after rummaging among their camp stores, and eating some crackers and canned peaches, the boys, having picketed their horses, turned in, rolled up in their blankets, and were asleep almost as soon as their heads were on the pillows, which were, as a matter of fact, stuffed with hay. An examination, next morning, disclosed nothing more in the neighborhood of the tunnel entrance than their own and, their ponies' feet marks, until Bud, with an exclamation, pointed to several cigarette stubs on the ground, and a number of half-burned matches. "Some one was here last night--or yesterday!" he declared. "And they stood in this one spot for some time--either resting or spying." "What would they be spying on!" asked Dick.