"Well, it isn't here." Dad was somewhat puzzled by this time. He saw that Stacy was very confident of having left the gun at that particular place, but it could not be found.

"Maybe somebody's stolen it," suggested the boy.

"Nonsense! Who is there here to steal it, in the first place? In the second, how could any one slip in here at the right moment and get away with your rifle?"

"You have no---no idea what has become of it---no theory?" asked the Professor.

"Not the least little bit," replied the guide.

"Most remarkable---most remarkable," muttered Professor Zepplin. "I cannot understand it."

"We'll look around a bit," announced Dad.

The three men searched everywhere, even going all the way down to the base of the rise on either side, but nowhere did they find the slightest trace of the missing rifle. After they had returned to the summit, Dad, a new idea in mind, went over the rocks and the ground again in search of footprints. The only footprints observable were those of their own party. There was more in the mystery than Dad could fathom.

"Well, this gets me," declared the guide, wiping the perspiration from his forehead. "This certainly does."

"Is---is my rifle lost?" wailed Chunky.

"I reckon you'll never see that pretty bit of firearms again," grinned Jim.

"But it must be here," insisted Stacy.

"But it isn't. Fortunately we have plenty of guns with us. You can get another when we go back to camp."

"Yes, but this one is mine-----"

"Was yours," corrected Nance.

"It is mine, and I'm going to have it before I leave this miserable old hole," declared the boy.

"I hope you find it. I'd like to know how the thing ever got away in that mysterious manner."

"Maybe the lion took it."

"Mebby he did. Funny I hadn't thought of that," answered Nance gravely.

Then both he and the Professor burst into a shout of laughter.

They made their way slowly back to the point where they were to meet the others of the party. Chunky, now being without a rifle, was well content to remain with the guide and the Professor.

While all this was going on Tad and Walter were picking their way over the rough ridges, through narrow canyons, riding their ponies where a novice would hardly have dared to walk. The ponies seemed to take to the work naturally. Not a single misstep was made by either of them.

They, too, could hear the dogs, but the latter were far away most of the time, even though, for all the riders knew, they might have been just the other side of the rocky wall along which the two boys were traveling.

They kept on in this way until late in the afternoon, when they stopped and dismounted, deciding that they would have a bite to eat.

"It doesn't look as if we were going to have any luck, does it, Tad?"

asked Walter in a disappointed tone.

"No, it doesn't. But one never can tell. In hunting game you know it comes upon one suddenly. You have to be ever on the alert. We know that the dogs have been on the trail of something."

"Perhaps deer," suggested Walter.

"Yes, it is possible, though I don't know whether those dogs will trail deer or not. You know they may be trained to hunt lions. I didn't hear Mr. Nance say."

They were munching biscuit and eating oranges as they rested, which must have tasted good to them. The temperature was going down with the day, though the light was strong in the canyon where they were standing. Above them the jagged, broken cliffs rose tier on tier until they seemed to disappear far up in the fleecy clouds that were drifting lazily over the Canyon.

All at once Silver Face, Tad's pony, exhibited signs of restlessness, which seemed to be quickly communicated to the other animal. The pintos stamped, shook their heads and snorted.

"Whoa! What's wrong with you fellows?" demanded Tad, eyeing the ponies keenly. "Smell something, eh?"

"Maybe they smell oats," suggested Walter.

"I guess not. They are a long way from oats at the present moment."

Tad paused abruptly. A pebble had rattled down the rocky wall and bounded off some yards to the front of them. Silver Face started and would have bounded away had not a firm hand been at that instant laid on the bridle rein.

To one unaccustomed to the mountains the incident might have pa.s.sed unnoticed. By this time Tad Butler was a pretty keen woodsman as well as plainsman. He had learned to take notice of everything. Even the most trivial signs hold a meaning all their own for the man who habitually lives close to Nature.

The lad glanced sharply at the rocks.

"See anything?" asked Walter.

"No."

"What did you think you heard?"

"I didn't hear anything but that pebble. The horses smelled something, though."

While he was speaking the lad's glances were traveling slowly over the rocks above. All at once he paused.

"Don't stir, Walt. Look up."

"Where?"

"In line with that cloud that looks like a dragon. Then lower your glance slowly. I think you will see something worth while."

It was a full moment before Walter Perkins discovered that to which his attention had been called.

"It's a cat," breathed Walt, almost in awe.

"Yes, that's a lion. He is evidently hiding up there, where he has gone to get away from the dogs. We will walk away a bit as if we were leaving. Then we'll tether the horses securely. Don't act as if you saw the beast. I know now what was the matter with the mustangs. They scented that beast up there."

The ponies were quickly secured, after which the boys crouched in the brush and sought out the lion again. He was still in the same place, but was now standing erect, head toward them, well raised as if in a listening att.i.tude.

"My, isn't he a fine one!" whispered Walt. Walter Perkins was not suffering from the same complaint that Chunky had caught when he first saw his lion over in the other canyon, an offshoot from the Bright Angel Canyon, and where he had lost his rifle so mysteriously.

"Take careful aim; then, when he turns his side toward us, let him have it," directed Tad.