"Where?"

"To the top of the cliffs."

"Dangerous. Mighty dangerous. I hope they come back all right," Wilson said.

He shook his head, clasped his hands behind his back, and walked in circles before his cave.

"Commander Wilson," Frank began slowly, "have you seen any people prowling around Honeycomb Caves?"

Wilson stopped short and looked Frank squarely in the eyes. "I'm alone. A hermit. That's what I am. I haven't seen anybody. n.o.body comes near me. They think I'm queer."

Joe described both Todd and Quill. "Have you seen anyone resembling them?" he persisted.

"No. But come to think of it, there was a fellow-"

The Hardys looked alertly at the old sailor. Had he seen one of the missing men?

"Yes, go on," Frank encouraged. "What did he look like?"

"The first one you mentioned."

"Todd?"

"Yes. I once knew a fellow like that. He was second mate on my cruiser in the Philippines."

Joe turned aside and made a wry face as the man continued: "Come to think of it, his name was Todd. Yes, it was," the commander went on. "He shipwrecked me deliberately and I had to climb a pineapple tree until the natives stopped beating their drums and went home."

Joe leaned close to Frank and said in a low voice, "He's off again. What'll we do now?"

As Commander Wilson rambled on, Frank edged closer to the mouth of the cave and glanced inside. He gave an involuntary start as he saw something he had not noticed before. But before he could whisper to Joe, Wilson wheeled about. "A man's cave is his castle," he said tartly.

Frank tried to manage a grin. "Well, I guess we'd better be going, Commander," he said. "Those fellows must have caught a fish by now."

Without saying a word, the old salt went into his cave. The Hardys continued down the beach again.

When they had gone a dozen yards, Frank seized Joe's arm and pulled him behind a large rock.

"What's the matter, Frank?"

"Joe, I saw a cap in Wilson's cave-the same foreign style that was dropped by the fellow at the radar site!"

"Do you think there's some connection?"

Frank suggested that they hide and watch the old fellow's cave. "You notice he got mighty excited when I looked into his quarters."

"I'll bet he's got something in there he doesn't want us to see," he said, peering over the rock. Suddenly he hissed, "Watch it! Here he comes!"

The two boys crouched low. Joe poked his head around the boulder for a quick look. "Frank, he's going down the beach the other way-probably to look in our cave."

"Now's our chance to explore his," Frank said. "Is he out of sight yet?"

"Yes."

Frank and Joe scrambled out of their hiding place and dashed into Wilson's cave.

"Boy, is it ever deep!" Joe exclaimed. "It goes way back!"

"And look here," Frank said, picking up the cap from the floor. "This could be more than a coincidence."

"Wow! He's got an a.r.s.enal, too!" whispered Joe. He pointed to a shotgun lying on a rock ledge.

"So that's where the mysterious shooting came from," Frank guessed. "And how about this?"

He picked up a dog-eared notebook from beside the gun and leafed it.

"It's a code book! Let's take it to the light so we can study it."

The boys had been well schooled in cryptography by their father. Eagerly the two moved nearer the mouth of the cave.

All at once the interior darkened and Commander Wilson stood at the entrance! "Spies! You're all spies!" he boomed. "Give me that book, you-you young pirates!"

As Frank and Joe stood tongue-tied, Wilson lunged toward the stone ledge.

"Look out!" Joe cried out. "He's going for the shotgun!"

CHAPTER XIII.

A Straight-Line Clue FRANK dropped the code book and leaped to intercept Commander Wilson before he could reach the shotgun. But the old man was as agile as an athlete! He dodged and twisted out of Frank's way like a piece of spring steel and grabbed the weapon.

"Frank! Run!" Joe shouted as he ducked toward the front of the cave.

Realizing it was now impossible to cope with Wilson, Frank dashed after his brother. But as the two boys reached the cave mouth, there was a loud explosion. Frank stumbled and fell to the ground.

"You killed him! You killed my brother!" Joe cried out. He bent down over the prostrate form. But instead of finding blood on the back of Frank's red shirt, Joe saw a large, round white patch. At the same time Frank shook his head, got to his knees, then stood up.

"Are you all right?" Joe asked. Out of the corner of his eye he saw the smoking shotgun in Wilson's hand.

The old man had a gleeful expression on his face.

"I'm okay," Frank said. "Let's get out of here!" The boys retreated halfway to the water's edge before stopping.

"The blast knocked me down," Frank said, reaching about gingerly to touch his back. "What was the gun loaded with?" He removed his shirt and the brothers examined it closely. "Joel This looks like flour! It is flour!"

"So that's what Wilson used for ammunition!" Joe said. "Now I know for sure he's a candidate for the b.o.o.by hatch."

With mixed feelings of embarra.s.sment and chagrin, Frank donned his shirt and the Hardys looked back as Wilson emerged from the cave. Again he shook his fist.

"That's what you spies get for snooping around Commander Wilson's cave!" he shouted. "You have some nerve trying to read the code book of the Queen's Navy!"

"We were only looking at that funny cap," Frank called back. "Where did you get it?"

"In Rockaway, of course-where I get all my supplies," Wilson said. "That's where I go when the Queen's Navy forgets to send the supply ship."

Shaken by the weird incident, the brothers headed for their cave.

"That cap will bear some investigating," said Joe.

"You're right," Frank agreed. "If they're sold at the general store in Rockaway, maybe the Bayport prowler bought his there too."

"Look who's coming," said Joe. They glanced up to see Chet and Biff scrambling down the ravine toward them. Biff had a monster of a fish slung across his shoulder.

"Hi, fellows!" Chet called out. "Look what we caught!"

Joe grinned. "It's almost as good as a whale!"

Puffing and beaming, Chet and Biff hastened up to the Hardys. The sea ba.s.s which Biff carried weighed more than thirty pounds.

"Will we chow down today!" Chet said gleefully, then added quickly, "And I discovered a mine, too."

"A gold mine, I suppose," Joe said.

"I don't know what kind," Chet said seriously, "but my detector picked up some funny noises "

"Chet's right," Biff said. "Somethings buried up there. Fellows, you ought to go hear for yourselves. I'll show you the place."

"Okay. You win," Frank said skeptically.

"I'll cook some of the fish while you're gone," Chet said. He added wistfully, "I wish we had some flour to sprinkle on it."

Frank gulped and Joe pounded him on the back "Did I say something wrong?" Chet asked.

"Oh, no!" Frank said hastily. "Give us the detector, Chet."

Joe took the device and in a few minutes the three boys were clambering up the ravine toward the top of the cliff.

When they reached it, Joe donned the earphones and held the detector several inches off the ground.

"Over there," Biff directed. Joe went toward the spot. A moment later he winced as a clicking chattered like a machine gun in his ears.

"No kidding, there is something underneath here," he said. "Listen for yourself, Frank."

Frank complied, then moved the detector from right to left. "That's strange," he muttered. "This nine, or whatever it is Chet discovered, runs in a straight line."

"Maybe a water pipe," Biff said. "Wouldn't that be a joke!"

"A water pipe from where to where?" Joe countered. "Why put a drain underground at a place like this?"

"Whatever the thing is," Frank said, "it lies east to west, apparently from near the coastline to the highway."

"I've got an idea," Joe said. He moved to a stand of pine trees growing several hundred yards back from the precipice and selected the tallest "Give me a boost, Frank."

After getting a lift from his brother, Joe shinned to the first branch, scrambled to the top of the tree, and looked intently westward.

"What do you see over there?" Frank called up.

"You'd be surprised!" said Joe.

"Come on," Biff said. "You're tracing an imaginary line. What does it point to?"

"The Palais Paris," Joe replied. In a few moments he was back on the ground. "Frank, I have a strange feeling about that place. Let's investigate it."

"Not this minute," his brother replied. "I'd like to do some digging."

"But with what?" asked Joe.

"I'll get some tools," Biff volunteered. "Johnny the fisherman will lend us his." He hastened off and returned presently with a shovel and pickax over his shoulder.

The boys took turns wielding the pick and shovel. Rocks and dirt flew up out of the hole they fashioned.

But they reached three feet down without striking metal.

Biff leaned on the shovel and ran his thumb along his brow like a windshield wiper. "We might dig all day and not find anything," he said. "Frank, do you suppose it is a metallic substance which makes the detector click like that?"

"I'm not sure," Frank replied. "It might be an electrical conduit. Let's check in Rockaway."

"Okay." Joe chuckled. "As soon as we've eaten that feast Chet's preparing for us."

The boys left the tools near the edge of the cliff where they could find them, then retreated down the ravine to the cave. Chet had made a spit, on which large chunks of the freshly caught sea ba.s.s were broiling over hot coals "Smells great, Chet," Joe said. "Let's eat and be on our way."

"We're going back?" Chet asked in dismay.

'To Rockaway for the time being," said Frank, and told what they had observed on the cliff top.

"Then I did find a good clue, eh?" Chet asked proudly. "First the pistol and now this. What would you fellows do without me?"

"We'll make an operative out of you, like Dad's a.s.sistant, Sam Radley," Frank said.

"Just so long as it isn't dangerous," Chet said, and pa.s.sed out portions of the succulent fish. Frank, Joe, and Biff had to admit it was one of the finest meals they had ever tasted.

"It's great brain food," said Chet. "I think we're going to need it on this case of yours," he added with a wink at the Hardys.

"Don't worry," Biff said. "They'll get to the bottom of this-someday."