“Was it a diamond?” Bob asked.
Jupiter grinned. “It’s a diamond all right, just as I thought. A large industrial-type diamond, not worth much; but the expert in Los Angeles was most surprised when I told him where I had discovered it. He found it pretty difficult to believe. He said he would have thought it was an African stone. I left it with him for various tests. He will call me here as soon as he completes his study.”
“Wow!” Pete exclaimed.
“Did you get the candles and sombreros?” Jupiter asked.
“We sure did,” Pete said.
“And a book about Moaning Valley,” Bob added.
The two boys told Jupiter about their trip to Santa Carla and the car that had forced them off the road.
“Did you get the licence number?” Jupiter asked immediately.
“Believe me, Jupe, there wasn’t time,” Pete said, “but I did notice that it was a different plate — sort of blue and white.”
“Hmmmmm,” Jupiter mused, “probably a Nevada plate. And you say the scar-faced man looked down at you?”
“Probably came back to finish the job, but the other cars scared him off,” Pete said angrily.
“Perhaps,” Jupiter said thoughtfully. “And you also saw the professor in town?”
“And Old Ben and his partner, Waldo,” Bob pointed out.
“Of course the top of the pass is only a few miles from here,” Jupiter mused. “Anyone from the ranch or the valley could have driven up there in just a few minutes and probably not have been missed.”
“Gee, I guess so,” Bob agreed.
“Still,” Jupiter went on thoughtfully, “a Nevada licence plate is most interesting. As far as we know, no one around the ranch has anything but a California plate.”
“You mean there’s someone around here we don’t know?” Pete said.
“Sure there is,” Bob told him. “That man with the eye patch.”
“It looks that way,” Jupiter agreed, “but now we must get to work. I’ll look through that book on Moaning Valley while you two go down and check the scuba equipment. Wrap the tanks in something that will disguise them, and then put them on the bikes with the candles, the sombreros and the bundle I brought.”
“The plan!” Bob and Pete said together. “What is it?”
“I’ll tell you on the way,” Jupiter said, and looked at his prized chronometer. “We have to hurry now if we’re going to reach Moaning Valley before sundown. To-night we may solve the mystery of Moaning Valley!”
Half an hour later the First Investigator appeared in the barn, waving the book at Bob and Pete.
“I think I’ve found part of the answer,” Jupiter announced. “It says here that about fifty years ago they sealed up many of the old mine shafts in Devil Mountain. They had never found any gold or anything else, so they closed the tunnels. Fifty years ago was when the original moaning sound stopped!”
“You mean one of them has been opened up again?” asked Bob. “And the wind blowing through it causes the moaning sound?”
“Yes, I think so,” Jupiter agreed. “The question is how and why?… Are you fellows ready?”
“Ready, Jupe,” Pete said.
“All right, then put on the sombreros before we ride out of the barn,” Jupiter instructed.
The boys donned the wide-brimmed straw hats, balanced the heavy tanks disguised in burlap sacks, and mounted their bikes. The bikes proved somewhat hard to handle with the weight on them, and it was clear that they would have to pedal with care.
“Ohhh,” Bob cried, wincing with pain.
“Is it your ankle, Bob?” asked Pete.
“It’s all the weight on the bike,” Jupiter decided.
Bob nodded unhappily. “I don’t think I can make it, Jupe. I guess I’ll have to stay behind.”
Jupiter had his thoughtful look. “No, I don’t think you will have to stay behind, Bob. Perhaps we can turn this misfortune into an advantage. It will make our deception more convincing.”
“What deception?” Pete asked, bewildered.
“The classic military tactic of the camp-fires and logs that look like cannon,” Jupiter explained obscurely. “Bob, unload your scuba equipment. Without the weight I think you can operate the bike.”
Bob tried again and found that without the extra weight he could indeed pedal satisfactorily. The boys rode out of the barn towards the gate. As they passed the house Mrs. Dalton waved from the porch.
“Have a good time, boys, and don’t stay out too late!” she called. “And be careful!”
Once out of sight of the ranch, the boys pedalled faster towards Moaning Valley. When they reached the place where the road ended at the iron gate, they dismounted and carried their bundles and their bikes into the thick bushes.
“Now,” Jupiter said, “here is my plan. We’re going to get inside the cave without being seen.”
Pete nodded. “I get it. We’ll take the moaning by surprise.”
“Right,” said Jupe. “Of course, if my theory is correct we’re being watched closely right now!”
“Gosh,” Bob said, “then how do we do it?”
“We go under water,” Jupiter told them, “using the scuba equipment. I checked on the tide and it’s higher this evening. I estimate that most of the tunnel from the beach will be under water.”
“But, Jupe,” Bob objected, “how will we get into the water without being seen if we’re being watched now?”
Jupiter beamed triumphantly. “We will use the decoy tactic. The way armies used to light camp-fires at night, and then slip away in the dark.”
“But — ” Pete began.
“You see,” Jupiter went on, “I also noticed last night that while the trail to the right is in clear view from the top of Devil Mountain, the trail to the left is hidden. Come on. Walk casually and in the open.”
The three boys climbed over the iron gate and continued down the cliff path to the left. When they were just out of sight from the top of Devil Mountain, Jupiter said, “Stop here.” The boys put down the scuba tanks, and watched as Jupiter opened the secret package.
“That’s just old clothes!” exclaimed Pete.