Mr. and Mrs. Dalton looked impressed. Jupiter’s correct use of so many big words always made adults think that he must be older than he actually was. Bob and Pete, however, were aware that Jupe had more on his mind than a walk along the beach. They tried to look as wide-awake as possible.
“Well… ” Mrs. Dalton began dubiously.
“Why not, boys?” Mr. Dalton decided. “It’s early, and I expect the first night on a ranch is too exciting to be wasted in sleep.” He turned to his wife. “Do them good, Martha. Better to look around the beach to-night, because I’ll be keeping them pretty busy starting tomorrow.”
“All right then,” Mrs. Dalton smiled. “Off with you, but no later than ten o’clock. We get up early here.”
The three boys did not wait for further talk. They carried their cookie plates and milk glasses to the kitchen and went out the back door.
As soon as they were out of the house, Jupiter started to give instructions. “Pete, you go to the barn and get that long coil of rope I saw hanging there. Bob, you go up to your room and get our chalk and our flashlights. I’ll get our bikes ready.”
“Are we going to the cave, Jupe?” Bob asked.
“Right. That is the only place to solve the mystery of Moaning Valley.”
“The cave?” Pete gulped. “Now? Couldn’t we see more in the day-time?”
“The moaning only happens at night,” Jupiter pointed out, “and when you’re inside a cave day-time doesn’t make any difference. Besides, the cave doesn’t moan every night. We know that it’s been moaning to-night, and if we don’t go now we might have to wait for days.”
By this time the other two were convinced. They moved swiftly into operation, and shortly afterwards the three boys met at the ranch gate.
Pete tied the long coil of rope to his luggage carrier, and they bicycled away along the narrow dirt road. The night was warm and the moon was up now, shining down on the silvery road that lay ahead.
Although the Crooked-Y Ranch stretched for miles along the shore of the Pacific Ocean, the sea itself was hidden by the coastal mountains. In the moonlight the rocky mountains were tall and silent, and the green live-oak trees looked like pale white ghosts. As they rode, the boys could hear the herds of cattle moving restlessly in the fields, the horses snorting and whinnying close to the road.
Then suddenly, without warning, the eerie moan floated out across the valley.
Bob scrambled to his feet. “Are you all right?” he asked anxiously.
Pete stood up. “I think so. Are you, Jupe?”
Jupiter got up more slowly and brushed at his clothes. His eyes had that faraway look that they always got when he was thinking.
“I was unable to move. A most interesting mental reaction,” he mused. “It’s similar to the way a small animal becomes paralysed when a snake looks at it. The animal literally can’t move, and is easily caught when it could have escaped.”
Bob and Pete both stared at their friend as he coolly analysed such a narrow escape from injury. Jupiter gazed up at the side of Devil Mountain in the moonlight.
“There seem to be many loose boulders up there,” Jupe observed, “and the mountain-side is very dry. I imagine it’s quite common for rocks to fall here. The naval gunnery probably loosened them in many places.”
The three boys approached the big rock. It was buried deep in the ground only a few yards from the entrance to El Diablo’s cave.
“Look, there are marks on it!” Bob was pointing at the boulder. “Gosh, Jupe, do you think someone pushed it down on us?”
“There are some marks,” Jupiter said after he had examined the rock more carefully. “Of course that is not so surprising.”
“It hit against a lot of other rocks on its way down,” Pete pointed out.
“We didn’t see anyone up there,” Bob said.
Jupiter nodded. “Still, someone up there might not want to be seen.”
“Gee, maybe we better go back,” Pete said.
“No, but we’ll be even more careful,” Jupiter said. “At least rocks can’t fall down a mountain at us when we’re inside the cave.”
With Jupiter in the lead, the boys entered the cave. They turned on their flashlights, and Bob marked the first question mark and arrow at the entrance.
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.”
Bob looked sceptical. “Maybe you were just nervous, Pete. We shouldn’t have split up.”
But Jupiter walked over to the wall where Pete said he had seen the black, shiny shape. He knelt down.
“Pete wasn’t just nervous, Bob,” Jupiter said. “Look here.”
Pete and Bob hurried to where Jupe was kneeling. There were two large, dark marks on the stone floor. Big, egg-shaped footprints that reflected the bright beam of the flashlight.
“What… ” Bob hesitated. “What is it, Jupe?”
“Something wet,” Jupiter said. “Water probably, but it might be something else.”
“Ugh,” Pete gulped.
Jupiter shone his light all across the floor. There were no other marks. The ceiling, too, was completely dry.
“There’s nothing else wet around,” he said. “Pete is right. Something was standing here. Something that left wet marks.”
“Marks that big? They must be two or three feet long!” Bob said.