"Gadzooks !" cried Jerry, mopping his face and looking towards the kidnappers. "They've gone!"

"They sure disappeared in a hurry," said Jerry. "I wish we could have captured them. Frank, how's your leg?"

"Oh, it'll be all right, but it hurts." He gave a wan smile. "Never mind that, though. The main thing is that we found Joe."

"Yes, thank goodness," his brother said weakly.

Chet had taken the Sleuth into deep water and was now speeding towards Bayport. Jerry and Biff were busy trying to make Frank and Joe comfortable on one of the long seats.

"To think I missed finding Joe!" Chet said in disgust. "I climbed those cliffs every other time and searched. When Joe was found, where was I? Sitting in the boat!"

"Good thing you were," Jerry retorted. "It's lucky for us someone was here to have the Sleuth ready for a fast getaway."

"Why did it have to be me?" Chet complained. "Some fellows have all the luck. Joe, tell me about your capture. Who were those men who shot at you and heaved all those rocks? When did they take you to the cave?"

"Better let Joe rest awhile," Frank advised.

"I think we ought to go back and clean up on that gang!" Jerry put in.

"I'd like to learn more about them myself," Frank said, "but I think we'd better leave it to the police.

Those kidnappers are a tough outfit, and we have Joe to look after. He's in bad shape. We should get him home."

"He looks hungry," Chet observed sympathetically, as Frank tuned in their radio and called police headquarters to report the rescue.

Joe opened his eyes. "You bet I'm hungry."

Chet grabbed the package of sandwiches he had brought with him and handed them to his chum. "I knew these would come in handy," he said. "Dig in."

"Hold it!" Frank warned. "No solid food until the doctor says it's all right."

"Then how about the milk in this Thermos?"

"Okay."

Joe drank the milk slowly and gratefully while Jerry satisfied Chet's curiosity about their experience in the cave rescue.

Chet whistled. "That was a close squeak."

When the Hardys reached home, their mother was overwhelmed with relief at seeing Joe safe.

Aunt Gertrude hugged her nephew and said, "Well, this time you deserve sympathy. At least you didn't do something harumscarum and propel yourself right into a mess of trouble."

Dr Bates, the family physician, was summoned to examine the young detectives. "No internal damage,"

he declared. "Just exhaustion. Joe'll be fit in just a day or two. Frank has a deep bruise which will be sore for a while."

Joe was given a steaming bowl of hot soup, then put to bed. He immediately fell asleep.

Frank related the story of the rescue and gave Aunt Gertrude credit for the clue. She smiled and blushed but said nothing.

It was not until late that evening, after he had been refreshed by a long, sound sleep, that Joe was able to tell the others what had happened to him. He still looked pale, but good food and rest were beginning to do their work and a trace of colour had returned to his cheeks.

"As you know," he said, "at Chet's party I chased into the woods after that man who was looking in our car boot. As I got near, someone reached out and grabbed me. I couldn't see his face."

Joe said a gag had been jammed into his mouth and a hand clapped over it. Then he was dragged to a car.

"Mercy!" exclaimed Aunt Gertrude.

"But why did he kidnap you if he was only after the secret radio?" Frank asked.

"There's another reason," Joe replied. "I'll come to that. When we got to his car I tried to fight him, but he's as strong as an ox and managed to tie me up and put me in the back seat.

"Then he drove away. We went down the road for some distance and stopped. Two men came out of the bushes and walked over to us. One said, s that you, Gross?' and my captor growled at them, 'No names.' When they saw me in the car, the men wanted to know who I was. It seems they didn't know Gross was going to kidnap me."

Joe said there had been a row about it. The other two men had wanted Gross to bring him back, but he was stubborn. "This kid knows too much," Gross had said. "He saw the rocks. Besides, his father is a detective."

"The other men called him a fool and said he should have left me alone and let the other thing go.

"One of them told Gross they didn't want the authorities after them for kidnapping. Then they realized it was too late to let me go, because there would be trouble when I got back to Bayport and told my story."

Joe said that the two men got into the car and they all rode for about two miles. Then one of the men climbed out and headed across a field towards the bay.

"We went on, but we hadn't gone far when Gross lost control of the wheel and we crashed into a ditch.

The car was wrecked but no one was hurt. Gross and the other man seemed worried because they were afraid somebody would come along and find them. They took off the licence plates.

"Gross knew there was an old inn nearby. They agreed to go to it and telephone a friend of theirs to bring a saloon. They took a blanket out of the car. We walked up the road and into a lane where the inn was.

Without any warning one of them slugged me from behind."

Frank said, "And put you in the blanket."

Joe said that later, as he started to come to in the inn, a drug was forced into his mouth and he was made to drink some water. He pa.s.sed out, and did not wake up until morning, when they were carrying him in the blanket to their friend's saloon.

"Just as we drove out of the lane and on to the Gresham road," Joe continued, "I heard a car coming and managed to raise up. It looked like ours, so I tried to signal. Then Gross shoved me down."

Joe had been driven to Sh.o.r.e Road and taken to the cave through an abandoned shaft.

"You were there nearly two whole days!" Frank said.

"Most of the time I was alone. They fixed up a few sacks for me to lie on, but they didn't pay much attention to me. Once in a while they would bring in sandwiches and water and feed them to me."

"Did you find out what they're up to?" Frank asked.

"At night, when they thought I was asleep, I overheard enough to learn one of the gang's secrets. They're smugglers!"

Aunt Gertrude opened her mouth wide. "Smugglers!" she gasped. "What kind?"

"Diamonds and electronic equipment. That's probably why they wanted to get Mr Wright's special radio."

Joe paused and Mrs Hardy asked if he were too tired to go on. "No, I'm okay, Mother. I also learned that one of the top men is named Chris. From what was said, I'd guess he's that big fair-haired man who's been watching us."

Frank was excited by this news. Now they had something definite to go on! If Joe were right, they could concentrate on finding Chris and turning him over to the police.

Joe spoke up. "There are four or five in the gang working with Chris, and others offsh.o.r.e. Chris delivers smuggled diamonds. His pals in the cave-one tall and dark, one red-haired, and one short-mentioned that he had diamonds in his briefcase. Chris thought we had seen them when the case burst open. Gross saw a chance to kidnap one of us to keep us from talking."

"A stupid move," Frank commented. "Even if we had seen the diamonds, we wouldn't have known they'd been smuggled. What about Mr Wright's secret radio? Did they talk about that?"

"I'm not sure," Joe answered. "Gross mentioned a secret gadget, but since they smuggle. electronic equipment, it could be anything. Do we still have the transistor?" he asked.

"Yes. But it's my guess someone connected with the smugglers figured out that we have the radio and thought it might be in our boot. Do you know the names of any of the others in the gang?"

Joe shook his head. "I'm sure there's a big boss, but they never mentioned him. One man who came to the cave had a nasal voice. He sounded like one of those burglars at Mr Wright's house."

"And he's afraid of someone named Shorty," Frank added. "This is a real clue." After a moment he said thoughtfully, "So we're up against a gang of smugglers."

"I think," Aunt Gertrude said firmly, "that you boys should leave well enough alone. Joe is back safe and sound, and we ought to be satisfied. If you try tracking down those smugglers, you'll only end up in trouble. Leave it to the police."

The conversation was interrupted by the ringing of' the telephone. Frank answered the call.

"Are you one of the Hardy boys?" a strange voice asked.

"Yes. Who is this?"

"The inventor of the secret radio."

"What's your name?" Frank asked.

"You know I don't want to mention it on the phone. All I want to find out is whether you still have it," the man replied.

Frank was suspicious at once. He beckoned his mother and wrote on the telephone pad, Go next. door and try to have this call traced. Then call the police and give them Joe's clues to the kidnappers.

Aloud Frank was saying, "Why are you so interested, sir?"

"Cause I'm the inventor and I want the radio back." The stranger spoke sharply.

A long parley followed. Finally, when Frank was sure his mother had had time to call the police, he said, "Sorry not to help you, sir, but you'll have to get your information from my father. He isn't here right this minute."

"Your father!" the man shrieked. "Why, you impudent young pup! I'll be right over and you'll give me that radio or I'll-I'll-"

The caller hung up.

CHAPTER IX.

Smuggler's Trail THE evening pa.s.sed with no further word from the mysterious caller who had phoned from a public booth but had disappeared before the police could track him down. Frank and Joe discussed the situation.

"Maybe he was scared off," Joe suggested. "And what about the secret radio? Somebody may look in the boot again."

"Right," Frank agreed. "I'll bring it in here. But each time we leave the house let's take the invention along."

Before the family went to bed, Mrs Hardy turned on the burglar alarm, which was connected to every door and window in the house and garage. There was no disturbance during the night.

"We're safe so far," Frank remarked at breakfast, "Maybe the police have caught Chris and the others.

I'll phone Chief Collig."

"Sorry, Frank," came the report from headquarters. "None of my men has picked up a clue."

Almost a week pa.s.sed. Still there was no news. The kidnapper-smugglers had covered their tracks well.

Joe had recovered from his experience and Frank's injured leg had healed. The brothers were ready to continue their sleuthing. They asked Chet, Jerry, and Biff to help them.

"Gross and the others may sneak back to Bayport," Frank prophesied. "They'll get nervy soon and we may have a chance to trip them up."

"Where do we go from here?" Biff asked.

"A tour of the docks," Frank answered, "to hunt for a whaler."

A long but wary search of Bayport's busy waterfront yielded nothing. Finally all the boys went home.

Frank and Joe found that Aunt Gertrude had been shopping. "Who is that new young man working in Bickford's jewellery shop?" she asked abruptly.

"I never saw a young man working in there," Frank replied. "The only a.s.sistant I know of is elderly and he's in the hospital right now."

"A young man, I said," Aunt Gertrude repeated in a tone that did not invite contradiction. "A very suspicious-looking young man. He wasn't there the last time I went in."

"He's new to me," Joe remarked. "What happened?"

"You see this diamond pin I'm wearing?" Aunt Gertrude pointed to a small one on the shoulder of her dress. "Well, he kept eying it while I was looking at some inexpensive watches."

"He was probably just admiring it, Aunty," Frank suggested.

"Admiring it, yes. With the thought of stealing it!" Aunt Gertrude was warming to her subject. "You can't fool me about young men. Besides, I've seen that a.s.sistant somewhere before."

"Where?" Joe asked.

"I'm not sure, but I know I have seen him."

"Is that all you have against the poor fellow?' Frank asked jokingly.

"It's enough. Mark my words, that young jewellery a.s.sistant is bad. Next thing we hear of him he'll be in prison for robbing his employer!"