Then he crept through the underbush until he felt it was safe to stand up and walk. He kept a good distance from the road, for he did not want to be seen. He felt it was very important that he get back to tell the Daltons what Pete and Jupe were doing in the cave. If Old Ben had actually found a diamond mine, they could be in real danger!
Bob hurried through the night as fast as he could with his injured leg and the difficult terrain. Before he had gone more than a few hundred yards he heard a soft sound in the night. It was a car driving slowly along the dirt road — without lights! It stopped no more than fifty feet from where Bob crouched.
A shadowy figure got out and walked rapidly towards Devil Mountain. The dark shape was dressed completely in black, and was all but invisible in the night. It quickly vanished.
Bob crept up to the parked car. It had a Nevada licence plate.
Deep inside Devil Mountain, Pete and Jupe continued to track the moaning sound. After the first tunnel, they had come to another cavern and had again used their candles to locate the passage out. In the third cavern, smaller than any of the others, they had found three passages with air blowing through them. They decided not to split up. Instead, they searched each passage together.
The first tunnel ran straight ahead for quite a distance, then made a sudden, sharp turn.
“It’s heading back towards the ocean, Jupe,” Pete observed.
Jupiter frowned. “I don’t think we want to go that way. I’m sure the moaning sound comes from closer to the valley side.” He checked his compass. “We should go east or north-east, I think.”
“This tunnel is heading south-west.”
The boys retraced their steps and tried the second passage. Soon it, too, curved away towards the southwest. Once again they went back to the cavern. Pete was becoming impatient.
“Golly, Jupe, we could walk around in here for ever!”
“Yes, but, I’m sure we’re on the right track. The moaning gets louder every time we move east.”
Reluctantly Pete followed him into the third passage. The air current was strong and the moaning much louder. The tunnel went straight east! Jupiter pushed ahead as fast as was safe with only their flashlights. Suddenly both boys stopped in their tracks.
There was a gaping hole in the left wall, where a side passage joined the tunnel they were in.
“Gosh,” Pete said, “that’s the first side tunnel we’ve seen.”
“Yes,” Jupiter replied, examining it with his flashlight, “and it’s manmade — an old mine shaft that wasn’t sealed at this end. Pete, look!”
The flame of Jupiter’s candle was blowing strongly outward.
“What does that mean, Jupe?”
“It means,” Jupiter whispered excitedly, “that somewhere down there is a third opening to the outside! Probably one of the old mine entrances has been secretly opened.”
“Then why didn’t the sheriff find it? Or Mr. Dalton?”
“I’m not sure, Pete,” Jupiter admitted, “but — ” His eyes suddenly widened as he listened to something.
Then Pete heard it, too — a faint sound of digging.
“Come on,” Jupiter whispered, and started into the new passage.
As Pete prepared to follow, he suddenly became aware of the sound of footsteps behind him.
“Jupe,” he quavered weakly.
Standing there, close behind them, was a small, thin man with burning dark eyes and a proud face — the face of little more than a boy. He wore a black sombrero, a short black jacket, a high-necked black shirt, and tight black trousers that flared at the bottom above shiny black boots.
He was the young man in the picture Professor Walsh had shown them at the ranch. El Diablo!
And he held a pistol in his left hand.
“Yipes!” cried Pete.
El Diablo pointed his pistol at Pete and made a sharp cutting motion in the air with his other hand.
“He wants us to be silent,” Jupiter said, a little shakily.
El Diablo nodded. His boyish face showed no expression at all. He motioned with the pistol that he wanted the boys to walk ahead of him in the direction from which they had come, away from the sound of digging.
Reluctantly the two boys obeyed. They retraced their steps through the dark tunnel until they came to a cavern, where El Diablo motioned them to the right.
They walked and walked, along passages and through caverns. Although Pete knew by his watch that they had travelled for less than five minutes, it seemed more like five hours as he plodded along behind Jupiter. El Diablo, with his pistol, stayed just behind them.
“Halt!”
The command came sharply just as Pete and Jupiter entered another cavern. It was the first word El Diablo had spoken and it had a muffled, hollow sound.
The boys stopped. This cavern was smaller than most they had been in, and it had a gloomy, dank atmosphere.
“There!” El Diablo commanded in his muffled voice.
The bandit gestured towards a very narrow opening in the cavern wall. Jupiter and Pete looked at each other grimly, but there was nothing they could do. They marched into the narrow tunnel, with El Diablo close behind. They had taken only about ten steps when they came to a mound of rocks that completely blocked the passage. A dead-end! Pete and Jupiter turned in dismay.
El Diablo’s face was as rigid as stone. With a motion of his pistol, he indicated that they were to stand along the left wall. Then he quickly bent over and rolled a large rock away from the mound.
“Come!” the muffled voice commanded.
The boys walked to the hole that had been opened in the end of the passage, and Pete peered in. He saw nothing but a black hole. Before he could shine his flashlight inside, a strong shove sent him sprawling into the dark opening.
Pete landed hard on a stone floor. Something struck him in the ribs, and then he heard the stone being rolled back. Pete lay in total darkness behind the wall of rock.
“Pete?” It was Jupiter’s voice beside him.
“I’m here,” Pete answered, “but I wish I wasn’t.”
“I’m afraid he’s walled us in,” Jupe whispered in the darkness.
“I’m just plain afraid,” Pete said.
At the edge of Moaning Valley, Bob was hurrying towards The Crooked-Y Ranch. Behind him, as if to spur him on, the valley continued to moan.
“Aaaaaahhhhhhhh — oooooooo — oooooo — oo!”