Jupiter turned his head and listened intently. The sound seemed to come from the wall of the cavern.
“It’s… inside the mountain!” Jupiter said.
Bob protested. “It can’t be, Jupe. It has to be from another part of the cave.”
Jupiter shook his head. “If my sense of direction is correct, the other part of the cave is to our left,” he said. “We are facing the side of the mountain — and no tunnels go in that direction!”
“Maybe we better get out,” Pete suggested.
“I think,” Jupiter said hurriedly, “Pete is right. Let’s go!”
The boys pushed pell-mell against each other in their scramble for the narrow exit. Pete reached the small tunnel first and began to crawl through. Jupiter and Bob followed right behind.
They tumbled out into water up to their knees, and floundered across the flat rocks till they sprawled at last on the white sand of the beach. They lay there panting.
“Where did that noise come from?” Bob finally broke the silence.
“I don’t know,” Jupiter admitted reluctantly. “But I think we’ve done enough exploring for one night. Let’s start back.”
Bob and Pete were only too glad to follow the First Investigator back up the narrow trail. They had nearly reached the iron gate at the top of the cliff when Jupiter suddenly stopped. In the darkness Pete almost ran into him.
“What are you doing, Jupe!”
Jupiter didn’t reply. He was staring up at the twin peaks of Devil Mountain.
“What is it?” Bob asked in a whisper.
“I just had an idea,” Jupiter answered slowly. “And I also thought I saw something move up there on the mountain where — ”
The sound of jingling carried across the night along with the clip-clop, clip-clop, clip-clop of a horse’s hoofs.
“Oh no!” Bob groaned.
“Is that what we heard inside the cave?” whispered Pete.
“I think so,” Jupiter said. “The sound must have filtered down through some crevice in the rock of the mountain. Sound carries very clearly that way. It would have seemed as if it was inside the mountain itself.”
The boys crouched down in the thick bushes near the gate as the hoof beats came closer. Then a great black horse appeared on the steep slopes of Devil Mountain. It came down the mountain at a trot and passed within a few feet from where the boys crouched in the bushes.
“There’s no rider!” Bob whispered.
“Should we try to catch it?” asked Pete.
“No, I don’t think so,” Jupiter replied. “Let’s wait.”
The boys crouched silently under cover of the bushes. Suddenly Pete stiffened, and pointed towards the slope. A man was coming down the mountain at a fast walk. As he passed their hiding place, they had a clear view of him in the moonlight. He was a tall, dark man with a long nose, a ragged scar on his right cheek, and a black patch over his right eye!
“Did you see that eye patch?” hissed Pete.
“And the scar,” Bob added.
“I was more interested in his suit,” Jupiter whispered. “It was definitely a business suit, and unless I am mistaken I think he had a pistol under his coat!”
“Can’t we go now, Jupe?” said Pete nervously.
“Yes, I think we’d better,” Jupiter agreed. “This has been a most interesting night.”
Pete and Bob needed no urging. As they hurried along the road to where they had left their bikes, they kept looking behind them anxiously. But they saw nothing else. While they were riding past the end of Moaning Valley, however, a long wail echoed through the night.
“Aaaaaaaaaaaahhhhhhhhh — ooooooooooooooo — ooooo — ooo!”
The boys began to pedal furiously in the direction of the ranch house.
8
El Diablo!
Pete woke up in bright sunlight. Confused, he looked around the unfamiliar room. Where was he? Then a horse whinnied somewhere outside, a cow lowed, and Pete remembered that he was in the upstairs bedroom of The Crooked-Y. He leaned over the edge of his top bunk to see what Jupiter was up to. Jupiter was not there.
Pete sat up quickly, bumping his head on the low ceiling.
“Ouch!” he grunted.
“Shhhhhh!” Bob hissed from his bunk across the room, and pointed towards the window.
In front of the window Jupiter sat cross-legged on the floor, looking like a small Buddha in his bathrobe. A large sheet of paper was spread out on the floor in front of him and in the middle of it he had stacked four books. On the paper Jupiter had drawn a lot of pencil lines.
As Pete stared down at the books and the paper and the pencil marks he realized that Jupiter had made a rough model of Moaning Valley. He had marked the cave entrances in pencil.
“He’s been sitting like that for an hour,” Bob explained.
“Gosh,” Pete said. “I couldn’t sit like that for ten minutes!” The intense concentration of their stocky friend always awed Bob and Pete.
Suddenly, Jupiter spoke. “I am ascertaining the exact topographical arrangement of Moaning Valley, Pete. The key to our puzzle lies in the physical pattern.”
“Huh?” Pete said.
“Jupe means that he thinks the mystery can be solved by studying the lay of the land,” Bob explained.
“Oh,” Pete said. “Why didn’t he say so?”
Ignoring Pete, Jupiter went on, “The real mystery of Moaning Valley is why does the moaning stop when we go inside? It happened twice last night, yet when we were leaving the area the moaning began again.”
He held up a newspaper. “I have here a newspaper report of the sudden recurrence of the moaning. In it the sheriff says that the main reason no one has been able to identify the cause of the moaning is that once inside they never hear it any more.”
Jupiter put down the paper. “I’m convinced now that the moaning doesn’t stop by accident!”
“I guess you’re right,” Bob said. “The way it started again right when we were leaving sure looks like someone was watching us.”
“But how does that — uh — model help us, Jupe?” Pete blurted out.
Jupiter looked down at his crude model. “I’ve marked all the places we were last night. Now we know that both times we entered the cave the moaning stopped instantly. It happened too quickly for it to have been someone inside the cave who was watching us.”
Bob nodded eagerly. “I get it! So we had to be seen before we went in.”
“Exactly,” Jupiter said, “and from my model I’ve deduced that we could have been seen everywhere we went from only one place — the top of Devil Mountain.”
“Then all we have to do is tell Mr. Dalton someone is up on Devil Mountain and let him catch the person!” exclaimed Pete.
Jupiter shook his head. “No, Pete, no one would believe us unless they caught the man and it would be almost impossible to get to the top without being seen. Whoever is up there would just run away.”
“Then — ” Bob began.
“How — ” Pete started at the same instant.
“We will have to observe what is actually happening in the cave,” Jupiter said solemnly, “so that we can tell people the full story.”
“But we don’t know what’s happening in the cave,” Pete objected. “Do we?”
“No, but I’ve got a plan in mind,” revealed Jupiter, “and I’ve got a clue as to what it’s all about!”
“You do?” Pete said. “What is it?”
“Last night I found this in one of the passages,” Jupiter explained, holding up the rough, blackish stone he had found in the mine-shaft passage. “The passage was once a mine shaft, and I found this stone just where it ended in one of those blockages.”
Bob took the little stone, looked at it with a puzzled expression and passed it on to Pete.
“But what is it, Jupe?” Pete demanded. “I mean, besides a kind of hard, slippery stone?”