It is a pleasure to welcome you on the set of the latest mystery starring those three lads who call themselves The Three Investigators. In the event that you have not become acquainted with them in their previous appearances, allow me to introduce Jupiter Jones, Pete Crenshaw, and Bob Andrews, all of Rocky Beach, California, not far from the fabled city of Hollywood.

Some time ago the three formed the detective firm of The Three Investigators to solve any mysteries that came their way. Head of the firm is Jupiter Jones, who is known for his logical mind, his cool head, and his stubborn refusal to let any riddle get the better of him. The Second Investigator is Pete Crenshaw, whose athletic skill serves the firm well in times of danger. The third and most studious member of the trio is Bob Andrews, who attends to research and record keeping. The firm makes its headquarters in a mobile home trailer hidden away in The Jones Salvage Yard, run by Jupiter’s aunt and uncle.

“We Investigate Anything” is the boys’ motto, and this time they prove it by journeying to a ranch in the California mountains to look into a cave that moans, a legendary bandit who refuses to stay dead, and some very strange happenings in a deserted valley. What they find will keep you biting your fingernails on the edge of your chair if you are the nervous type, so beware!

And now, enough of a preview. The case is about to unfold. Lights! Camera! Action!

ALFRED HITCHCOCK

“Aaoooahhhhhh — ooooooooooooo — ooooo — oo!”

The eerie moan rolled out across the valley in the twilight.

“That’s it,” Pete Crenshaw whispered. “It’s started again.”

Pete, Jupiter Jones and Bob Andrews were crouched on a high ridge in a remote corner of the Crooked-Y Ranch, just a few hundred feet from the Pacific Ocean.

The moan came again, long, drawn-out and chilling. “Aaaaaaaaaaahhhh— ooooooooooo — oooo!”

A shiver ran up Pete’s spine. “I don’t blame the ranch hands for not wanting to come here any more,” he said to his companions.

“Maybe it comes from the lighthouse we saw on the way,” Bob suggested in a low tone. “Maybe it’s some kind of echo from the foghorn.”

Jupiter shook his head. “No, Bob, I don’t think it’s the lighthouse. The sound is not that of a fog-horn signal. Besides, there isn’t any fog this evening.”

“Then what —” Bob began, but Jupiter was no longer crouched beside him. The stocky First Investigator was trotting off to the right along the ridge. Pete and Bob leaped up and followed. The sun was almost gone now in the crevasse between the coast mountains, and a hazy purple light hung over the valley.

Jupiter stopped after some fifty yards. The moan came again. He listened carefully, his hand cupped behind his ear.

Pete stared, puzzled. “What are we doing, Jupe?”

Jupiter didn’t answer. Instead he turned and walked almost a hundred yards in the opposite direction.

“Are we just going to walk all over this ridge, Jupe?” Bob asked, as puzzled as Pete by Jupiter’s strange actions.

Before Jupiter could reply, another eerie moan floated through the valley. “Aaaaaaaaaahhhhhhh — ooooooooo — oooo!”

Jupiter turned to them. “No, Bob, we’ve completed the experiment.”

“What experiment?” Pete blurted out. “We haven’t been doing anything but walk!”

“We have listened to the moan from three different points on this ridge,” Jupiter explained. “In my mind I drew imaginary lines from where I listened to where the moans appeared to originate. Where the three lines crossed is the exact source of the sound.”

Bob suddenly understood. “Sure, Pete,” he said. “It’s called triangulation. Engineers use it all the time.”

“Precisely,” Jupiter said. “Of course, the way I did it was very rough, but it will serve our purpose.”

“What purpose, Jupe?” asked Pete. “I mean, what did we find out?”

“We have found that the exact source of the sound is that cave in the mountain — El Diablo’s Cave,” Jupiter announced.

“Gee, Jupe,” Pete exclaimed, “we knew that already. Mr. and Mrs. Dalton told us.”

Jupiter shook his head. “Good investigators do not accept what other people report without checking it themselves. Witnesses are often unreliable, as Mr. Hitchcock has told us many times.”

Jupiter referred to the motion picture director, Alfred Hitchcock, who been a good friend of The Three Investigators ever since they had embarked on their adventures by trying to locate a haunted house for him to use in a film.

“I guess you’re right,” Pete said. “Mr. Hitchcock did show us how little witnesses really see.”

“Or hear,” Jupiter added, “But now I have no doubt that the moaning does come from El Diablo’s Cave. All we have to do is find out what is moaning, and —”

The stocky boy did not finish his sentence, for the moan rolled out once more — weird and chilling in the deep twilight of the shadowy valley. “Aaaaaa — hhhhhh — ooooooooooooo — oooooo — oo!”

Even Jupiter shivered this time, as long shadows began to creep across the valley.

Pete swallowed hard. “Gosh, Jupe, Mr. Dalton and the sheriff have searched the cave three times already. They didn’t find anything.”

“Maybe it’s some kind of animal,” Bob volunteered.

“It doesn’t sound like any animal I ever heard,” replied Jupiter, “and, anyway, the sheriff and Mr. Dalton would have found traces of any normal animal. They’re expert hunters and trackers.”

“Any normal animal?” Pete repeated uneasily.

“Maybe it’s some animal no one knows is here,” Jupiter said. “Or maybe,” and the First Investigator’s eyes sparkled, “it’s El Diablo himself!”

“Oh, no you don’t!” Pete cried. “We don’t believe in ghosts — do we?”

Jupiter grinned. “Who said anything about ghosts?”

“But El Diablo’s been dead almost a hundred years,” Bob objected, “If you don’t mean a ghost, Jupe what do you mean?”

Jupiter did not get a chance to answer, for at that moment the sky beyond the valley was suddenly lit up by bright red flashes. The boys’ eyes widened as explosions seemed to shake the whole valley.

“What is it, Jupe?” asked Bob.

Jupiter shook his head. “I don’t know.”

The flashes stopped and the echo of the explosions faded away. The three boys looked at each other. Then Bob snapped his fingers.

“I know, it’s the Navy! Remember when we were coming up on the truck, Jupe, we saw all those Navy ships on practice manoeuvres? I’ll bet they’re having target practice out in the Channel Islands.”

Pete laughed with relief. “Sure, they do that a couple of times a year. I read about it in the newspapers. They fire at some uninhabited island out there.”

Jupiter nodded. “It was even in the papers yesterday. Night firing practice. Come on, I want to get back to the ranch and find out more about this valley.”

Bob and Pete needed no urging for the valley had grown completely dark now. The three boys walked to their bikes, which were parked on the dirt road behind them.

Suddenly, from across the valley, they heard a loud rumbling sound, followed by a long wail.