"Yes," Frank answered. "And the FBI."

"Your father! He should be told about this at once!"

"But we can't reach him," Frank reminded her.

The hours dragged on into early evening. Mrs Hardy continually walked the floor, saying over and over, "This is dreadful, dreadful!"

Frank paced around nervously, mulling over in his mind the events that had taken place during the past two days. The telephone rang. Was it the kidnapper calling? Frank rushed to answer the call.

"Frank, this is Chief Collig!"

"Yes, Chief! Any news?"

"Not much. The police managed to detect the scratched-off serial number on the engine block of the car lying in the ditch. It was traced through the State Bureau of Motor Vehicles. The car was stolen yesterday evening from a man in Lewiston. No one saw the thief."

"Well, we're right back where we started," Frank said.

After a light late supper, Frank settled himself into a wing chair within reach of the telephone. The hours ticked by with no word from Joe or his abductors. Finally, through sheer exhaustion, Frank dozed off.

When he awoke, the sun was already sending bright, warm rays into the room. Frank got up and began to pace back and forth. He and his mother ate a sketchy breakfast. They grew more uneasy when the morning pa.s.sed without any news of Joe.

Shortly after noon a taxi stopped in front of the Hardy home. A tall, angular woman, carrying a small suitcase, got out of the cab and hurried towards the house.

"It's Aunt Gertrude," Frank announced to his mother.

"I'm glad to be home!" Miss Hardy exclaimed as she entered the house like a rush of wind.

She glanced at Mrs Hardy and immediately sensed that something was troubling her. "Laura! You look exhausted. Haven't you been getting enough sleep? What's wrong?"

"We have something to tell you," Frank declared. "You'd better sit down."

He broke the news about Joe's disappearance as gently as he could. His story, however, sent Aunt Gertrude springing from her chair.

"That's terrible! Poor Joe! Call the police!" she cried. "Call the FBI! Do something!"

"Try to be calm," Frank pleaded. "The police and the FBI have already been notified."

"I felt it in my bones!" Aunt Gertrude exclaimed. "Something like this was bound to happen."

"Now, Gertrude, please," Mrs Hardy interrupted.

Aunt Gertrude continued to rattle on. "You can't be too careful these days. The world is full of rude and nasty people. Now you take this morning, for example, when I was walking on the platform at Gresham.

Suddenly this big, fair-haired man stepped right in front of me, carrying a bulging briefcase. Part of its zipper was torn and some of the papers inside were sticking through.

"Well, this clumsy ox gave me a hard bang on my arm with that dirty, beat-up briefcase. I was about to give him a piece of my mind, when he deliberately pushed me aside!"

Her words had seized Frank's attention. The man sounded like the one that Chet had stepped on in the airport terminal and Frank and Joe had chased later. He might be one of the kidnappers! The suspects'

car had gone towards Gresham!

"Then came the crowning insult," she went on. "He called me-he called me-an old whaler! Can you imagine? I never fished for a whale in my life! Next, this big, fair-haired lummox walked over to two other men and handed them the briefcase," Aunt Gertrude continued. "I was so furious, I decided to demand an apology. I went up to the big man and tapped him on the shoulder. He must know me because just then he said 'Hardy'. Well, he turned and glared at me, then hurried off with his friends. The nerve, indeed!"

Frank had already jumped to his feet: He was obviously excited. "Did you see what was written on the papers in the briefcase?"

"I wasn't close enough to read them. But one had red and blue stripes on it."

"He's one of the men we suspect!" Frank cried out. "Aunty, did you hear any more of the men's conversation? Anything at all?"

"No, not really," she answered, somewhat puzzled by her nephew's questioning. "I only caught a word or two. The fair-haired man said something about caves. Yes, that's it - caves! I remember because it struck me at the time that with his bad manners, he should be living in one."

Frank darted to the telephone and called Chet. "I'm sure I've latched on to an important lead," he told his chum. "I'll need your help."

"I'm ready to go any time you say."

"Okay! I'll be right over!"

CHAPTER VI.

Fogged In FRANK leaped into the convertible and headed for the Morton farm. He began piecing together the details of Aunt Gertrude's story about the fair-haired man at Gresham. He had said, "Hardy!"

"I'm sure he didn't mean Aunt Gertrude. He could have meant Dad or Joe!"

Then the man had made a reference to caves! There were many to be found in the cliffs which formed the north sh.o.r.e of Barmet Bay. Was Joe being held in one of them? Frank smiled, recalling his aunt's indignation at being called an "old whaler" by the big fair-haired man.

"He might not have been referring to whales at all," Frank thought. "There's a small, flat-hulled motorboat known as a motor whaler. Maybe that's what he had in mind."

Frank told himself that using such a term would be unusual for any person unless he was familiar with boats. The young sleuth was certain that he had a real lead at last!

As Frank drew up before the Morton house, Chet came down the steps at a run. "What's up?" he asked eagerly.

Frank repeated Aunt Gertrude's story of the man mentioning the name Hardy and making the mysterious reference to whaler and caves.

Chet whistled, then suddenly his eyes widened. "You mean Joe might be a prisoner in a sh.o.r.e cave?"

"Exactly!" Frank answered. "And I'll search every one of them if I have to!"

"I'm with you! How about the other fellows? Let's get Biff and Jerry to come along. They'd be mad as hornets if they weren't in on the search."

"Okay!" Frank replied. "We'll use the Sleuth." This was the Hardys' sleek motorboat.

"Let's go!" Chet said briskly. Then the ever-present problem of food occurred to him. "If you'll wait a few minutes I'll ask Mom to fix up a lunch for us. We may get hungry. At least you may, but I'm sure I will."

Both boys dashed into the house. While Mrs Morton was making up a package of sandwiches and cake, Frank reached Jerry and Biff by telephone and gave them an inkling of what was afoot. They were eager to help and promised to be at the Hardy boathouse within twenty minutes.

In a short time Chet was ready and scrambled into the convertible beside Frank. At the boathouse Jerry and Biff were waiting for them. Biff was a tall, lanky blond whose perpetual good humour was indicated by the slight tilt to the outer corners of his lips. Jerry, medium height and dark, was wiry and more serious. Both boys were agog with curiosity.

"What's the clue?" Jerry asked, and Frank gave the details as he unlocked the door of the boathouse.

The boys quickly unmoored the Sleuth and jumped aboard. The engine spluttered spasmodically a few times, then burst into a roar. Frank opened the throttle and the craft shot into the bay, gradually increasing speed.

"If we don't find Joe, then what?" Jerry asked.

Frank answered promptly, "Go down the coast tomorrow. There are a few caves along the beach. You fellows game?"

"You bet," they chorused.

There were clouds in the sky and far off towards the open water at the distant end of the bay was a hint of fog. Frank eyed the mist doubtfully. It would take some time to make a close search of the caves on the north sh.o.r.e, and if fog came up, a hunt would be difficult. Chet, thinking the same thing, mentioned it aloud.

"We'll just have to hope for the best," Biff spoke up.

As they zipped along, the boys talked over Miss Hardy's encounter with the fair-haired man.

"He may be tall," said Biff, "but he sure sounds short on brains!"

"He'll need all the brains he has if we get on his trail," Chet affirmed.

"But why would he be mixed up in Joe's disappearance?" said Biff. "Surely he wouldn't kidnap Joe just because Chet stepped on him."

"There's something deeper behind it," Frank said, thinking of the secret radio, "but I'm not at liberty to tell you fellows. Sorry."

The Sleuth sped on towards the north sh.o.r.e and gradually drew closer to the high cliff's that rose sheer from the waters of the bay. The fog was coming up the bay now in a high, menacing grey wall.

Chet grimaced. "We're not going to make it. That fog will be on us before we get within a quarter of a mile of the caves."

"I'm afraid so," Frank said. "But I hate to give up now that we've come this far."

"I've had a few experiences in fog out on this bay," Biff Hooper remarked, "and I don't want to repeat 'em if it can be helped. You never know when some other boat is going to come along and run you down. You can't see it until the boat's right on top of you. Let one of those big ships wallop you and you're done for!"

"A horn isn't much good," said Jerry, "because the fog seems to make the sound come from a different direction than the true one."

The fog swirled down on the boys, hiding the sh.o.r.e from view. It enveloped them so completely that they could scarcely see more than a few yards ahead. Frank had already turned on his yellow fog light and suddenly they saw a small tug a short distance up the bay. The craft was heading towards the city, but now it vanished. Frank reduced speed and pressed the horn. No sound!

"This," said Jerry, "is bad. If it weren't for Joe, I'd say go home. I wonder how long the pea soup will last."

No one ventured a guess. Frank said tensely, "Watch for that tug, fellows. My horn won't blow."

As the Sleuth groped blindly through the clammy mist, Frank thought he heard the faint throb of the tug's engines. His light did not pick up the craft and it was impossible to estimate its distance or direction.

Then came the blast of the tug's whistle, low and mournful through the heavy fog. It seemed to be far to the right, and Frank hoped to avoid it by going straight ahead.

When the whistle sounded again, it was louder and seemed to come from a point just to their left. It was drawing closer!

"That old tug must have travelled about two miles clean across the bay in half a minute," Chet remarked.

"Frank, 1-look out!"

As he spoke, the whistle sounded again. This time Biff straightened up in alarm. The tug seemed to be directly ahead.

"How do you figure its position, Frank?"

"I think the tug is mighty close. It's hard to tell where the sound's coming from. We'll just have to go easy and hope we see it first."

Biff could hardly make out the stern of the Sleuth. "This is worse than a blackout," he commented.

Once more the whistle blew, this time so terrifyingly loud that the tug seemed to be only a few yards away. The boys could hear its engines. Still their light revealed nothing.

"Up in front, Chet!" snapped Frank. "If you see it, sing out!"

Chet scrambled on to the bow and peered into the grey gloom ahead. Suddenly, he gave a yell of terror.

"It's bearing right down on us!"

Even as he shouted, a heavy dark shadow loomed out of the fog. The Sleuth was about to be rammed!

The tug was sweeping down on the boys. It was only a few yards away! The boys could see a man on deck, waving his arms wildly. The whistle shrieked.

No time to lose! The engine of the Sleuth broke into a sudden clamour as Frank opened the throttle wide. At the same instant he swung the wheel hard to port. The motorboat swerved and shot directly across the bow of the larger boat.

For a breathless second it seemed that nothing could save the boys. They waited for the jarring impact that seemed only seconds away!

But the Sleuth had speed, and Frank handled his craft masterfully. His boat shot clear!

The tug went roaring astern. It had missed the Sleuth with less than a yard to spare! The Hardys' boat was caught in the heavy swell and pitched to and fro, but rode it out.

Chet Morton broke the silence. "Wow, that was a close call!"

Jerry Gilroy, who had been thrown off balance when the Sleuth altered its course so suddenly, scrambled to his feet, blinking. "I'll say! Were we hit?"

"We're still here." Biff grinned. Nevertheless, he had been badly frightened. "That's the last time I'll ever come out on the bay when there's a fog brewing," he announced solemnly. "That was too narrow a squeak!"

Chet, now that the peril had pa.s.sed, leaned down from the bow. He shook hands with the other three boys, then gravely clasped his own.

"What's that for?" Jerry asked.

"Congratulating you and myself on still being alive." The others smiled weakly.

Frank steered the Sleuth back to its previous course. Again the boat crept towards the north sh.o.r.e, invisible beyond the wall of mist. Frank did not dare venture closer for fear of piling his craft on to the rocks at the foot of the cliffs. He cruised aimlessly back and forth, but within half an hour the fog began to lift. It thinned out, writhing and twisting like plumes of smoke.

"The cliffs!" Chet cried in relief as the boys caught sight of the land rising sharply just ahead. They were less than two hundred yards off sh.o.r.e and already far down the bay, abreast of the caves.

"We can make our search after all," Frank said.