Even with their flashlights on, they could see nothing but a long, dark passage that went straight into Devil Mountain. Its walls were smooth, and the ceiling was just high enough to permit Pete — the tallest investigator — to stand up. For a distance of about forty feet the passageway continued to be a straight tunnel with smooth stone walls. Then it suddenly opened into a large cavern.
The boys shone their flashlights all around the cavern. They were in a huge room with a towering ceiling. The far end of the cavern was so distant they could only just see it.
“It’s like a big city railroad station!” Bob exclaimed. “I never saw so big a cave.” His voice sounded hollow and faraway.
“Hello!” Pete called.
“Hello… hello… hello-ooooooo,” his voice echoed.
The boys laughed. The echoes seemed to bounce through the cavern. “Hello… hello-ooooo!” scouted Bob.
While Pete and Bob were shouting, Jupiter was inspecting the huge cavern more closely with the help of his flashlight.
“Look!” he suddenly called to them.
To their left, in the wall, was a small black hole—the opening of a passage that seemed to lead out of the cavern. The boys aimed their flashlights at the walls on both sides of the cavern. They saw many more openings — at least ten passages that led from the big cavern deeper into the mountain.
“Jeepers,” Pete said, “which way do we go?”
All the passages looked about the same — barely high enough for Pete to stand up in, and about four feet wide.
Jupiter frowned. “It is obvious that El Diablo’s Cave must be a large complex of passages and chambers all through the mountain.”
“Maybe that’s why the posse couldn’t find El Diablo,” Bob said. “There were so many passages that he could stay hidden.”
Jupiter nodded. “That seems a likely explanation.”
“How does a cave like this get started anyway?” Pete asked, looking around with awe.
“Water erosion mostly,” Bob explained. “I’ve read about it in the library. A mountain like this is made up of different rocks, some softer than the others. The water comes in and wears away the softer rock. It takes millions of years sometimes. A lot of this area was under water a long time ago.”
“Bob’s right,” Jupiter said. “But I’m not sure that all of these passages are natural. Some of them look man-made. Maybe by El Diablo’s men.”
“Or miners, Jupe,” Bob said. “I read how they used to look for gold around here.”
Pete was shining his light at first one passage, then another. “Where do we start looking?” he asked.
“It could take us months to search all these passages,” said Bob. “I’ll bet each one branches out again farther on.”
“Probably,” Jupiter agreed, “but fortunately we have an easy way to eliminate some of them. We’re looking for the moaning sound. All we have to do is listen at each entrance until we find the one where the moaning is coming from.”
“Hey, that’s right,” Pete said with enthusiasm. “We’ll just follow the moaning.”
“But Jupe… ” Bob was looking puzzled. “The moaning. I don’t hear it. I mean, I haven’t heard it since we came inside!”
The three boys stood perfectly still, listening intently. Bob was right — the cave was as quiet as a tomb.
“Jupe?” Pete said uneasily. “What does it mean?”
Jupiter shook his head in puzzlement. “I don’t know. Maybe it’s just a coincidence. Maybe it’ll start again soon.”
But the moaning did not start. Ten minutes passed and there was no sound inside the cave.
“I remember hearing it just before that rock fell, Jupe,” said Bob. “Only I wasn’t listening much after that.”
“We were too excited to think about it,” Jupiter said. “We can’t really be sure when it stopped.”
“Gosh,” Pete said, “what do we do now?”
“Perhaps it will begin again,” Jupiter said hopefully. “Mr. Dalton did say the cave moans irregularly. While we’re waiting, I think we should start to search the side passages one by one.”
Bob and Pete agreed. Anything would be better than just standing there in the spooky darkness. “Bob chalked a question mark and an arrow at the entrance to the first side passage, and the boys entered the tunnel.
They moved cautiously, their flashlights probing ahead until, less than thirty feet from the entrance, the tunnel suddenly ended. It did not end in a blank wall but in a pile of fallen rock that completely blocked the passage.
“Mr. Dalton said many of the tunnels were blocked by old earthquakes,” Bob recalled.
Pete looked worried. “Do you think it’s still dangerous?”
“No,” Jupiter said. “The ceilings are very solid. It took a heavy shock to make these rocks fall, and then only the very weakest places fell. This is a very safe cave.”
They retraced their steps, and tried the next four tunnels, carefully marking each entrance. All four passages ended in piles of fallen rocks.
“We’re wasting time,” said Jupiter finally. “We’ll split up and each search a passage. They seem quite safe.”
“We’ll each go through our tunnel until we can see the end,” Bob agreed, “unless it turns out not to be blocked.”
“That’s it,” Jupiter said. “If one of us finds a clear passage he can come back and wait here for the others.”
Quickly, each of the boys plunged into a tunnel, hopefully shining his flashlight ahead.
Jupiter found that his passage was natural for only a short distance. Then his flashlight revealed beams and braces that held up the walls, as in a mine shaft. He moved ahead cautiously for a few more yards, studying the floor and walls of the shaft.
Abruptly he came to a wall of rock and dirt that blocked the passage. Kneeling down to inspect the barricade more closely, he discovered a small, hard black stone that puzzled him. It was quite different from any stone he had ever seen. He stuck it into his pocket to examine later.
Just then a yell echoed through the passage.
“Jupe! Bob! Hurry!”
At that moment Bob was in another cavern similar to the first they had found. The tunnel he had been exploring had led him straight into another cavern. He was standing there dismayed because this one, too, had many small passages that led out of it. He had just decided to return to the first cavern and wait for the others when he heard Pete’s yell. Immediately he rushed back to the entrance of his tunnel.
Meanwhile, Jupiter was racing towards the mouth of Pete’s tunnel. Suddenly something came hurtling at him out of the dark. The next thing he knew he was sprawling on the stone floor with some wild creature clawing at him.
“Help!” a voice called in fright.
The voice was almost in Jupiter’s ear. It was Bob’s voice.
“Bob, it’s me!” cried Jupiter.
The hands that were clawing at Jupe relaxed, and the two boys shone their lights on each other.
“Gosh, I thought something had grabbed me,” Bob said.
“My reaction was the same,” Jupiter said. “It was a case of panic brought on by Pete’s call for —”
“Pete!” Bob cried.
“Come on!” said Jupe.
The two boys raced into the passage Pete had taken. The tunnel seemed longer than the others. They had been running for some distance before they saw a light ahead. It was coming from Pete’s flashlight.
“Here I am!” Pete called.
Bob and Jupiter burst out of the passage into still another large cavern. Pete stood in the centre, the beam of his flashlight trained on the left wall. He was looking pale.
“There was… something in here!” Pete stammered. “I saw it. All black and shiny!”
Bob and Jupiter focused their flashlights on the wall. They could see nothing at all.
“I tell you I saw something,” Pete insisted. “When I came out of the tunnel I heard a noise. I shone my light and saw… this… thing! Over there near the wall. It was big. I was so surprised I dropped my light, and when I picked it up the thing was gone.”