“Did you boys have a good walk on the beach last night?” Professor Walsh asked. “What did you find?”

“We had an interesting expedition,” Jupiter answered. “And we met a rather odd old man. He called himself Ben Jackson. Who is he, sir?”

“Old Ben and his partner, Waldo Turner, are prospectors,” Mr. Dalton explained. “I imagine they’ve looked for gold and silver and precious stones all over the West in their day.”

“According to local gossip they came here many years ago,” Mrs. Dalton added, “when there was a rumour that gold had been found. Of course, there never was any gold, but apparently Old Ben and Waldo never gave up. They have a shack on our land, and still consider themselves prospectors. They don’t seem to like to have visitors, but they don’t mind getting handouts from the ranchers around here. Of course, we call it a grubstake. They wouldn’t take charity.”

“They’re quite famous local characters,” Professor Walsh put in.

“They can really tell you stories,” Mr. Dalton smiled, “Of course, they’re somewhat eccentric, and most of their stories are just tall tales. For example, they’ll tell you about fighting the Indians, but I doubt if they ever did.”

“Gosh, you mean all that was a lie?” Pete exclaimed.

Before Mr. Dalton could reply, the back door of the kitchen burst open. The foreman, Luke Hardin, came in hurriedly.

“They just found young Castro out in Moanin’ Valley,” Hardin said grimly.

“Castro?” Mr. Dalton looked worried.

“Got thrown from his horse last night while he was riding herd on some strays. Lay there all night,” said Hardin.

“Is he all right?” Mrs. Dalton asked.

“Doc says he’s okay. They took him over to the hospital in Santa Carla.”

“I’ll go and see him right away!” Mr. Dalton jumped up.

“The men are kind of shook up,” Hardin added, his face dark. “Two more told me they’re going to quit. Castro was out in Moanin’ Valley and says he saw something moving. He took a look. Whatever it was spooked his horse. He was thrown and the horse ran off. He’s all bruised up and his ankle’s sprained.”

The Daltons looked at each other in despair. Jupiter spoke up.

“Was the horse a big black one, Mr. Hardin?” he asked.

“That’s right — Big Ebony. A good horse. Came back to the corral on his own this morning, so we knew to look for young Castro.”

Mr. Dalton spoke sharply. “Did you boys see Big Ebony last night?”

“Yes sir,” Jupiter said. “A big black horse without a rider.”

“You must always report a riderless horse on a ranch, boys,” Mr. Dalton said severely. “We would have found Castro sooner.”

“We would have, sir,” Jupe explained, “but we saw a man following him and assumed that he was the rider. He was a tall man, with a scar on his right cheek and an eye patch.”

Mr. Dalton shook his head. “Never heard of a man like that.”

“Tall and an eye patch?” Professor Walsh inquired. “Sounds menacing, but definitely not El Diablo, eh? He wasn’t tall, and he didn’t wear an eye patch.”

Mr. Dalton started for the door. “Luke, get the men calmed down if you can. I’ll join you in the north meadow after I see Castro. And I think I’ll talk to the sheriff about that man the boys say they saw.”

Jupiter spoke up again. “If you’re going into town, sir, perhaps you would take me? I have to return to Rocky Beach today.”

“Why, Jupiter, you’re not leaving us?” Mrs. Dalton asked.

“Oh, no,” Jupiter assured her. “It’s only that we need our scuba equipment. We saw some reefs offshore last night which look excellent for collecting specimens for our marine biology studies.”

Bob and Pete stared at Jupe. They did not remember that they had, seen any reefs, or that they were conducting marine biology studies. But they said nothing. They had learned not to question Jupiter when he had some scheme in mind.

“I’m afraid I don’t have time today to take you down,” Mr. Dalton said, “and I can’t spare a man or a truck. You’d better wait a few days.”

“That’s quite all right, sir,” Jupiter said. “If you’ll take me into town I’ll get the bus down. Someone will drive me back.”

“Better hurry up and get ready, then,” Mr. Dalton told him as he went out the door.

Mrs. Dalton looked at Bob and Pete. “I’m afraid you boys had better find something to do, too. With this trouble, Mr. Dalton won’t have time to work with you today.”

“We will, ma’am,” Bob assured her.

The boys went back to their room while Jupiter gathered what he needed for his return to Rocky Beach. As he packed, he revealed what he had in mind for Bob and Pete while he was gone.

“I want you to go into Santa Carla and buy a dozen large, plain candles,” Jupe said, “and three Mexican sombreros. With the Fiesta in Santa Carla there should be plenty of hats to buy. Tell Mr. and Mrs. Dalton you are going in to see the Fiesta parade.”

“Three sombreros?” Pete repeated.

“Right,” said Jupiter, without further explanation. “Then go to the library. Bob, I want you to learn all you can about the history of Devil Mountain and Moaning Valley. I mean all the exact details, not just legends.”

“I’ll find out all I can,” Bob assured the First Investigator. “What are you really going to Rocky Beach for?”

“To get the scuba equipment, as I said,” Jupiter replied, “and to take the diamond into Los Angeles to have it examined by an expert.”

Mr. Dalton called from below. “Jupiter! Ready?”

The boys hurried down, and Jupiter climbed into the cab of the pickup truck. As Bob and Pete watched him ride off, they realized that they still didn’t know what Jupe was planning to do with the scuba equipment.

After helping Mrs. Dalton in the kitchen for an hour or so, Bob borrowed Mrs. Dalton’s library card, and the two boys started off for Santa Carla on their bicycles.

“Enjoy the Fiesta, boys!” Mrs. Dalton called after them.

Actually, Bob and Pete were quite excited at the prospect of seeing the famous Santa Carla Fiesta, and they rode off in a holiday mood. The road from the ranch wound through the vast inland valley, surrounded on three sides by the brown mountains of Southern California. Away from the sea the sun was hot, and the boys noticed that all the creeks they passed were dry. At one point they crossed the wide bed of the Santa Carla River itself. Down below the bridge, the river bed was completely dried up, with small plants growing on its sun-baked surface.

Soon the highway began to climb towards San Mateo Pass. Bob and Pete had to get off their bikes and walk them around hairpin curves. Mountain valleys yawned close to the right, while rocky cliffs climbed steeply to the left. The boys walked slowly in the bright sun. After a long, hot hike they finally emerged at the top of the pass.

“Golly! Look at that!” Pete cried.

“Wow!” exclaimed Bob almost at the same moment.

Spread out before their eyes was a breathtaking panorama. The mountains sloped away to low foothills and then a wide coastal plain that spread in all directions to the blue water of the Pacific Ocean. The city of Santa Carla shimmered in the sun, its houses like tiny boxes in the great green expanse. Boats moved on the blue surface of the sea, and the mountainous Channel Islands seemed to float in the distance.

The boys were still staring at the magnificent sight when they heard thundering hoofbeats behind them. They whirled to see a horseman galloping down the highway straight at them. He rode a great black horse with a silver-mounted bridle and a silver-trimmed charro saddle, its enormous pommel horn glinting in the sun.

The boys stood transfixed as the horse bore down on them. The rider was a small slender man with dark eyes who wore a black sombrero, a short black jacket, flared trousers, and a black bandanna over the lower half of his face. He carried an ancient pistol that was aimed straight at the boys.