“At least,” Jupiter said solemnly. “Big and wet and shiny. Sort of a —”

“Monster!” Pete finished the sentence for Jupiter.

“The Old One!” Bob exclaimed.

The three boys looked at each other nervously. They did not believe in unknown monsters, but what could have made such big, wet marks?

Then a powerful glare of light fixed the three boys like moths against the wall. A harsh voice called from behind the dazzling light.

“What’s goin’ on here?”

A figure came slowly towards them — a bent, twisted figure with a wild white beard, carrying an enormous-looking rifle.

The old man pointed towards the dark tunnels that led from the cavern.

“Them passages goes a far piece inside,” he said in a high, cracked voice. “You young-uns could get lost mighty easy in there.”

The old man’s red-rimmed eyes gleamed wickedly.

“Got to be mightly careful here,” he croaked. “Got to know the country, yessir. Seventy years I lived out here, never lost my scalp. No sir. Got to think ahead, that’s the story. Know the country and fight the enemy.”

“Scalp?” Pete stared. “You fought Indians? Here?”

The old man waved his ancient rifle. “Injuns! I’ll tell you about Injuns, I will. Lived with Injuns all my life. Fine people but hard enemies, yessir. Almost lost my scalp twice. The country and Apache country. Sneaky, the Apaches. But I got away.”

“I don’t think there are any Indians now, sir,” Jupiter said politely, “and we won’t become lost.”

The old man’s eyes suddenly focused on the boys. For the first time he actually seemed to be seeing them. “Now?” he repeated. “Of course there’re no Injuns now. Are you boys crazy? You must be, wandering around in the cave. Strangers around here, eh?” His voice was lower now, and steadier, and he had lost his wild look.

Bob was the first to reply. “Yes sir, we’re from Rocky Beach.”

“We’re staying at The Crooked-Y with Mr. and Mrs. Dalton,” Jupiter explained. “Mr….?”

“Ben Jackson. You boys can call me Ben,” the old man said. “The Daltons, eh? Fine people, yes-siree. I was passing this old cave and thought I heard someone yell out. Guess that was one of you, eh?”

“Yes sir,” Jupiter said, “but we weren’t lost. You see, we mark our way so we always know how to get back.”

“Blaze a trail, eh? Well now, that’s mighty smart. I reckon maybe you would have been okay out in the big country in the old days. What are you doing in here, anyway?”

“We’re trying to find out what makes the moaning sound,” Bob explained.

“Only it stopped as soon as we came in,” Pete added.

Suddenly the old man seemed to crouch. His eyes clouded again, and grew wary. The change was so startling that for a moment the boys could almost imagine they were looking at a different person.

“Moanin’, eh?” Ben’s voice was high-pitched again. “Folks say it’s El Diablo come back. Not me, no sir. I say it’s The Old One, that’s what I say.

“The Old One lived in this here cave long before any white man showed up,” he went on. “Time don’t mean anything to The Old One. You boys stay out of here or The Old One’ll get you sure. Jess Dalton, he better stay out, too. The sheriff, all of them. The Old One’ll get them all!”

The old man’s voice crackled in the dark shadows of the cavern. Bob and Pete looked nervously at Jupiter, who was watching old Ben intently.

“Have you ever seen him, Mr. Jackson?” Jupiter asked. “The Old One, I mean? Have you seen him here in the cave?”

“Seen him?” the old man cackled. “I seen something, yessir. More’n once I seen it.”

The old man looked around warily, and then once again he changed. His twisted body straightened, his eyes cleared, his voice lowered and became calm.

“Well, you boys better come on out with me now. Can’t leave you yelling in here, eh?”

Jupiter nodded. “I think we’ve seen enough for now anyway. You’re quite right, it does seem easy to become lost in here.”

The old man picked up his electric lantern. Its bright light made the shadows of the cave seem far less menacing.

They soon found their way out into the quiet valley. As the old man walked them to their bikes, Jupiter cocked his ear towards the cave to listen. But the moaning sound did not come again. They thanked Ben Jackson for coming in to find them and said good night.

“You’re smart boys, yessir,” the old man said. “Only The Old One’s smarter than anyone. You boys better be careful. You tell Jess Dalton, The Old One is watching, yessir.”

The old man’s cackling laughter followed the boys as they rode down the dirt road in the moonlight. Rounding a curve, Jupiter suddenly stopped his bike.

“Oooff!” Pete grunted, narrowly missing him.

Bob stepped on his brakes. “What’s wrong, Jupe?” he asked.

“The Three Investigators do not give up until a job is completed,” Jupiter said, his bike already turned round and headed back the way they had come.

“I think we should go back to the ranch,” Bob said.

“So do I,” Pete added quickly.

“Two to one, Jupe,” Bob pointed out.

But Jupiter had already started pedalling back the way they had come. Bob and Pete watched for a moment, then began to follow him. They both knew there was no stopping Jupiter once he had an idea in his head.

When they caught up with The First Investigator, he was peering cautiously around the curve in the dark road.

“It’s all clear,” Jupiter said. “Come on.”

“What are we doing, Jupe?” Bob asked as The First Investigator got off his bike.

“We’re going to leave the bikes here and walk,” Jupiter explained. “We’ll try to keep out of sight.”

“Where do we walk to?” Pete wanted to know.

“I just noticed that this road curves around Devil Mountain towards the sea,” Jupiter explained. “I want to see if there is another entrance on the ocean side.”

Bob and Pete followed Jupiter down the dark road. The valley was shadowy in the moonlight. Shapes seemed to loom up out of the night as they walked — trees and boulders and dark gullies.

“There are three puzzles that have come to our attention to-night,” Jupiter said as they walked. “First, why did the moaning stop when we were inside the cave? I noticed that the wind was still blowing when we came out, so it wasn’t the wind that changed.”

“You mean something else made the moaning stop?” Bob asked.

“I’m sure of it,” Jupiter said firmly.

“But what?” demanded Pete.

“Perhaps something or someone who saw us,” Jupe replied. “Second,” he went on, “it seemed to me that Ben Jackson really wanted us to get out of that cave. I wonder why?”

“The way he changed was spooky,” Bob said, and he shivered, as if to prove it.

“Yes,” Jupiter mused, “he is a most peculiar old man. It almost seemed as if he was two different people living in two different times. In fact, I couldn’t help feeling that he was putting on some kind of performance.”

“Maybe he was really worried about us, Jupe,” Pete said. “I mean, if he really has seen… The Old One.”

“Perhaps,” Jupiter agreed. “And that’s our third problem — the black, shiny thing you saw, and those marks on the cave floor. I’m sure they were water marks. Of course there may be a pool in the cave, but it’s also possible that there’s another entrance to the cave on the ocean side. And that is what we’re going to look for!”

After the boys had walked a little farther, the road ended abruptly at an iron gate. Beyond it, two narrow paths, one to the left and one to the right, led down the rocky cliff. Far below, a white line of surf glowed in the moonlight. The boys climbed the fence and looked down over the steep cliff.

“We’ll go to the right, towards the cave,” Jupe said. “Pete had better lead and I’ll come last. We’ll rope ourselves together the way mountain climbers do. Then if we come to any difficult places, we’ll cross them one at a time.”