“Hal! Oh, Hal! Stop! This is Pickles.”

Hal stopped almost as suddenly as he had started to run. He recognized the cautious cry of his friend and waited for the four to overtake him.

“What you kids up to?” he inquired, after scanning the faces of the quartet. “I told you not to come, Pickles.”

“We’re not going to run away with you,” he replied. “We’re just going to walk a ways and then go back.”

“I’m glad to have you come, but you might get into trouble.”

“No, we won’t,” declared Frank with something of his old-time boastfulness. “We can get back any time before morning and nobody’ll ever see us.”

“Where you going to-night?” inquired Ferdinand.

“To the cave first.”

“In the caÑon?”

“Yes, I want to see if there’s any more of those nuggets there.”

“You haven’t any light,” reminded Byron.

“No, but I’ve got some matches.”

“I know where the lanterns are,” Frank announced. “They’re in the garage, and I can crawl in through the window. Let’s get them and explore the cave.”

“Yes, let’s do,” Ferdinand said eagerly. “Come on, Bad. You and I’ll go an’ get the lanterns, while the rest wait here for us.”

No objection being offered to this plan, Frank and Ferdinand made a dash back toward the garage. They were gone about fifteen minutes and returned with four lanterns. Then the march toward the caÑon was taken up.

Of course, there was much excited talk on the way. Every one of the self-appointed committee that was “seeing Hal off” expressed confidence in his integrity and all were highly indignant at Mr. Miles’ suspicions.

“He’d better go take a jump in the lake,” said Byron with unwonted vehemence. “He’s got no ’preciation of what you did for him.”

“Yes, if it hadn’t been for Hal, he’d probably never have got any of his specimens back at all,” observed Ferdinand.

“Somebody ought to slip him one,” declared Frank savagely.

“I don’t think he meant to be so hard on me,” interposed Hal charitably. “I was pretty sore at first, but when I saw how bad things looked for me, I wanted to get out. I wouldn’t have run away, but I don’t believe I could ever prove I wasn’t a thief. When you get in a fix like that, the best thing to do is to pack up and move.”

The interest the boys felt in the cave they were about to explore finally resulted in a change of subject, and Hal’s troubles were forgotten for the time being. In fact, Hal himself forgot much of the bitterness of his woes in the general eagerness of the conversation.

Arrived at the scene of their construction work in the caÑon, they lost no time in crossing the river and hastening up the walk to the waterfall cave. Outside the latter they stopped only long enough to light two of the lanterns. The other two they found without oil and set them aside. Then they crossed the second bridge into the cave.

Hal now assumed the leadership. He realized that the expedition was not without danger and felt the responsibility for the safety of his friends to be resting on his own shoulders. His first act, therefore, on entering the cave was to drive the other boys back several feet from the precipice and the roaring waterfall. Then he led them beyond the bend in the passage to the farther end of the cave, where the noise of the fall was not so deafening as to prevent conversation.

“You kids stay back here and explore this part while I go up in front and see if I can find any more of those nuggets,” suggested Hal, concealing by his manner his real motive in assigning them well back from the danger point. He knew that if he told them he was afraid they would get too close to the edge and fall over, some or all of them would be determined to hover close to the cataract.

Hal returned to the mouth of the cave with one of the lanterns. He could not help shuddering a little as he approached the edge of the precipice, and being of practical mind, he soon found himself speculating on a method of making this point more safe for visitors.

“There ought to be a fence or high railing along here to prevent people from getting too close and falling in,” he told himself. “If Dr. Byrd wants to invite people to visit this cave, he ought to make it safe. I think I’ll suggest this to him—”

His soliloquy was interrupted suddenly when he awoke to the fact that he was running away and did not intend to return to the doctor’s school.

“My, what a fool I am!” he exclaimed. “I think I’m losing my head. Really, I wish I wasn’t running away. I do hate to go. But—but—I’ve got to.”

He flashed his lantern about and began his search for the lost nuggets. He examined the floor and several crevices in the walls for fifteen or twenty minutes, but nothing rewarded his search. How the one nugget he had found got there was as big a mystery as the presence of the bag of souvenirs in the cave had been.

Finally he gave it up and went back to the farther part of the cave and rejoined the other boys. Byron and Walter were gazing upward at Frank and Ferdinand who were climbing up the wall on the right, which inclined like the side of a mountain. Fes carried the lantern.

“Look out, up there; don’t fall, or there’ll be some broken bones, and maybe necks,” warned Hal. “We don’t want any such accidents to-night.”

“We’re all right; just watch us,” answered Frank with his usual bravado.

“Where you going?” inquired Hal.

“As high as we can,” replied Ferdinand “Come on up. It isn’t steep. It’s easy climbing. You couldn’t fall in the dark.”

Fes and Frank were by this time fifty or sixty feet from the floor, and the light of their lantern still revealed no sign of a ceiling, or a converging of the walls overhead. This was rather astonishing, and Hal was moved with a desire to take part in the upward exploration.

“I’m going up, too,” he announced to Byron and Walter. “It doesn’t look steep and it’s rough enough to give a good foothold.”

“Let’s climb up with ’em, Pick,” suggested Byron.’

“All right,” answered Pickles, suiting the action to the word. In a moment all three were following the two leaders up the almost stair-like ascent. They climbed rapidly, for the success of Fes and Frank had given them confidence. Up, up, they went, Hal leading and Byron and Walter following in respective order.

Suddenly they were startled by a succession of cries from above. They stopped and looked upward apprehensively, and were surprised to see Fes and Frank standing on a ledge and looking down upon them.

“Come on, come on, kids,” yelled Frank. “We’re clear through the roof. It’s all open up here.”

Thrilled by this announcement, Hal quickened his steps and those behind him did likewise. In a few moments they had climbed up to where the leaders were waiting for them. Frank had spoken truly. They were standing on a level spot several yards in diameter; on one side arose a perpendicular wall of the mountain and on the other, far below, they looked down into the deep shadows of Mummy CaÑon.

“My! isn’t this great!” Hal exclaimed enthusiastically. “We’re real discoverers. Maybe nobody’s ever been up here before.”

“Nobody ever tried to climb Flathead, they say,” Byron observed. “I bet nobody ever got as high as this.”

“I wonder if we couldn’t climb higher from here,” said Fes, scanning the perpendicular wall.

“That doesn’t look much like it,” said Pickles with a laugh.

“I wish the moon’d come out so we could see farther,” said Hal. “I hate to come so far as this and stop.”

With these words, he flashed the rays of his lantern about. At one edge of the wall they found a break that looked like the mouth of a passage, but it was blocked by a large bowlder.

“I’m going to climb over it,” said Hal. “Here, Fes, give me a boost.”

Fes did as requested. With his lantern in one hand, Hal was boosted up to the top of the bowlder, which was about five feet through and perfectly round.

“Yes, there’s a passage here,” he announced. “Come on over.”

By a series of boosts, Byron, Frank, and Fes climbed over the big rock, the latter stopping on top of the bowlder to reach assistance to Walter. After they had passed this barrier, Ferd stopped to examine it more carefully and then said:

“Let’s try to push the rock over a little. It’s balanced here on a little neck. Maybe we can move it so we won’t have to climb over it when we come back.”

Hal had gone on ahead a short distance and paid little attention to this suggestion until he turned his head and saw his four companions with their shoulders to the bowlder.

“Hey! Stop! Stop!” he cried out frantically, realizing what would happen if they moved the rock.

But his warning was too late. Even as he screamed his command, the balanced rock toppled over and rolled heavily down the slight incline right into the mouth of the roof exit of the cave.

“Oh! if it would only go through!” was Hal’s wild wish. But it didn’t. The runaway sprang past his friends, lantern in hand, and made a hasty examination.

The bowlder was wedged fast, effectually blocking their only avenue of escape from the steep-walled mountain.