"Gee!" said Joe suddenly. "This really would be a swell hide-out for crooks. Maybe Lenny Stryker and the nurse, Martha Johnson, are being held in one of these empty houses."

Frank agreed. Since Doctor Lyall and the intern, Doctor Mills, had been taken in a car, the boys began to hunt eagerly for tire tracks. After a ten-minute inspection they came to a house at the far end of a dirt road, where a pa.s.senger car had been driven around to the side several times.

"Doctor Lyall said the room he was in seemed to have no windows," said Joe. "That could easily mean he was taken to a cellar."

"Let's walk around the house before we try to get in," Frank suggested.

Quietly the brothers followed the automobile tracks. They stopped at a cellar door. Joe nodded meaningly to Frank. The older brother crooked his finger to indicate they were to go on around the 141 house. Reaching the far side, the two boys stood gazing at the cellar windows over which black paper had been tacked.

"Shall we go in?" Joe whispered excitedly.

Frank nodded and started back toward the door. At the same instant he felt the ground give way. Joe had the same sensation. Then, before the brothers could jump aside, they were caught in a tremendous cave-in!

CHAPTER XVII.

Angry Customers.

the cries of the boys, mingled with the thudding sound of the cave-in, could be heard for some distance. A man who had just stopped his car in front of the empty house leaped out.

"What in thunder's going on here?" he asked himself, looking around fearfully.

All was quiet now. Yet he was sure the shouts he had heard were those of someone in trouble. Deciding the cries must have come from the rear of the house, he dashed forward.

When he beheld the area where the earth had collapsed, his eyes opened wide in horror.

"Great Scott!" he said. "That old brook must have opened up, and all the money I spent to fill it in, too!"

For the moment his thoughts were so occupied with his own problem that he completely forgot about the shouts he had heard. Below him Frank and Joe, holding their breaths until they realized it 142.

143 was impossible to do so much longer, were frantically clawing the loose dirt which had enveloped them. The man, seeing the heaving earth, suddenly came to his senses.

"Somebody's down there!" he decided in panic.

But how was he to help him?

Looking around wildly, he spied a large shovel and picked it up. Lying flat on his stomach at the edge of the cave-in, the man began tossing aside the dirt. Frank, about to lose consciousness, felt something hard near his upstretched hand. With a supreme effort the boy grabbed it.

It was only a matter of seconds until the stranger had pulled both Hardy boys from under the dirt. They lay on the ground, gasping for breath.

"Thank goodness, you're alive!" the man said in relief. "I don't know who you are, but I never should have forgiven myself if I hadn't reached you in time."

"Thanks," murmured Frank.

"Who-are-you?" Joe asked weakly.

The stranger explained he was the contractor for the new houses. Work was being held up on the project; that was why no men were on the job.

"I came over to see if everything was all right," he added. "I guess Providence must have sent me."

The contractor, a Mr. Smith, had a thermos bottle of hot soup in his car. After each of the boys had drunk a cup of it, they felt better. Joe thanked him and told the man who they were.

144 "Of course I've heard of your father," said Mr. Smith. "As a matter of fact, I've also heard of you boys." Smiling, he added, "I suppose you've been chasing some criminal."

"To tell you the truth, sir, we're after one now, and we thought he might be hiding in one of these empty houses. Do'you mind if we take a look?"

"Not at all. I'll let you in."

He took the Hardy boys through all the unoccupied houses, and watched in some amus.e.m.e.nt as the brothers tapped walls now and then.

"Guess you'll have to stick to old houses to find any secrets," he said indulgently. "I never build hidden closets or trap doors in my houses."

The boys' faces turned red. They had become so absorbed in their hunt for the mysterious secret panel they had not stopped to think such a thing would scarcely be installed in a house which was being built for speculation. They told Mr. Smith they were through their work, and thanked him for letting them look around. He drove the brothers to the center of Bayport and said good-bye.

"Just the same, Lenny Stryker might have been in one of those houses and been moved," said Joe defiantly.

"Sure," agreed Frank, "but that doesn't help us now. If he was moved, where is he?"

Joe shrugged. "We'd better work on something else," he said. "Say, Ben Whittaker's shop is just around the corner. Let's go talk to him."

145 The elderly locksmith was in the rear of his store. He greeted the boys solemnly, and told them he had heard nothing from his former helper, Mike Matton. The police had no trace of the stolen hardware. Worse than that, the fussy Mrs. Eccles was making matters very unpleasant for him.

"She threatens all kinds of things if I don't return her antique lock to her," Ben Whittaker said. "My reputation's going to be ruined."

"Oh, no," Frank spoke up quickly. "You've been in business here too many years for a little thing like that to make any difference, Mr. Whittaker."

"But it's not a little thing!" the man cried out. "There's Mr. Howard, and Mrs. Sommers, and------"

"You mean other people were robbed and are making trouble?" Joe asked.

"Plenty of them are," the locksmith replied worriedly. "In each case, Matton went to the house when no one was there but a maid. He used the same story he told you. Oh, what shall I do?"

The boys asked the man to give a description of the hardware which had been stolen from the homes of the indignant people. Ben Whittaker was able to tell them little, as he had never seen any of it.

"Let's go see the people, Frank," Joe suggested. "Maybe we'll be able to pick up a clue of some kind that way."

"Good idea," his brother agreed.

The first house at which they called was a large, attractive one. Mr, Howard was an architect and, 146 according to his own words, had put a great deal of thought into the building of a home for himself.

"One of my prize possessions was the knocker on the front door," he told the Hardys.

"The coat of arms of my family was embossed on it, and it was a fine piece of work. Why are you boys interested?" he asked suddenly.

Frank explained how the fellow who had removed Mr. Howard's knocker had almost been caught by them while tampering with the lock at their own home. "We'd like to track him down," he said.

"Well, I wish you luck!" the architect replied, rising to indicate that the interview was at an end.

Their next call was on a Mrs. Sommers. The woman appeared to be very much upset about the loss of the beautiful knocker which had been taken from her home.

"It was a very rare one," she told the boys. "I'm sure it never can be duplicated. I picked it up years ago in Europe."

"What value did you put on it?" Joe asked her.

When Mrs. Sommers replied that the knocker was insured for a thousand dollars, the boys jumped. The woman added that, though the insurance company would pay her for it, she never would be able to replace it.

After the boys left her house, Frank told Joe that this startling information had given him an idea. Mike Matton must be acquainted with someone who was collecting unusual door hardware. No legiti147 mate dealer would buy such things secondhand without knowing the seller, and it was doubtful that even a p.a.w.nbroker would take in such articles.

"Do you suppose," Joe asked as a thought came to him, "do you suppose Mike Matton could have sold them to the person Dad's looking for?"

"You mean the guy that gets into the museums with some strange invention?"

"Exactly."

The gang stole old and rare objects from museums, and it was possible that their leader was interested in valuable hardware too. Joe felt Mike Matton somehow might be mixed up with the museum thieves; perhaps as a sort of errand boy for the leader. This would account for the theft of the fingerprint data from Mr. Hardy's file, and also might explain the theft of the valuable hardware from Mr. Whittaker's shop and from the well-to-do residents of Bayport.

"Do you know what I think we ought to do?" Frank said. "Photograph the fingerprints on Dad's filing cabinet. Ours and Dad's will be there, of course, but there may be a strange set too."

Joe inquired how his brother expected to find out whether the marks might be those of Mike Matton. Frank said he would go to old Mr. Whittaker's shop to inspect things Mike Matton had handled.

The net result of this work was a surprise and added a new complication to the mystery.

The recent intruder into the Hardy home was not Mike Matton!

148 "More trouble," sighed Frank. "However, we've proved one thing. We probably have the fingerprints of the person who kidnaped Miss Johnson."

"Right you are," Joe agreed.

He suggested they leave the fingerprint work for a while and start out on the next job they were going to do; drive out to the Mead house and see if Chet's dory was there.

"Good idea. But let's stop and get Chet."

"You bet."

The brothers expected to find their stout chum either in the apple orchard or at the Morton icebox, but he was at neither place. No one was at home but Mrs. Morton. She seemed surprised to see the Hardys.

"I thought you boys would be over at the fair," she remarked.

"Fair?" Frank asked, puzzled.

"Oh, didn't you know about the county fair at Harlington? Chet went to it. I understand there are to be all sorts of amus.e.m.e.nts."

"Let's go, Frank!" Joe suggested impulsively. "We can have some fun and maybe find Chet."

The boys hurried to their roadster and sped away. A little later the outlines of a Ferris wheel came in sight.

"Quite a show," Joe remarked enthusiastically. "Shall we have some fun or try to find Chet right away?"

It was not necessary for the two Hardys to hunt 149 long for their friend. Not far from the entrance gate was a platform on which a man was announcing loudly: "Ten dollars, I said! Ten dollars! Easiest way in the world to earn ten dollars! All you have to be is smart!"

The barker held up a large padlock. "All you got to do is open this. Sure, it's a trick lock.

But it won't cost you a thing to try. Come on! Step this way, gentlemen!"

Frank nudged Joe. The first customer to ascend the stairs was Chet Morton!

CHAPTER XVIII.

The Lock Picker.

the crowd roared with laughter as Chet Morton struggled with the padlock. He was determined to win the ten dollars for opening it.

"Hi, fat boy, you better quit before you bust," cried one of the bystanders. Chet was bent double and was very red in the face.

"It'll cost you more than ten dollars for a doctor!" another shouted at him.

Frank and Joe were grinning from ear to ear. They knew their friend thought he could open the padlock because he had heard so much about locks and keys lately. But Chet Morton finally gave up the attempt.

"Who's next?" called the barker. He pointed his finger directly at the Hardys and added, "You look like a couple of bright fellows. How about coming up here?"

"I sure could use ten dollars," Joe replied, and pushed his way through the crowd.

150.

151 He, too, struggled with the lock, but to no avail. Disgusted, he handed it back and Frank ascended the platform.

"A free soda if you make it!" cried the first bystander who had kidded Chet.

Frank grinned. "And I'm thirsty, too. Sure hope I can win it, sir."

But Frank did not win the soda. As he gave up his attempts to open the lock, a tall man about thirty-five years old elbowed his way through the crowd and came up the steps.

Without saying a word he took the lock in his hand, held it near his ear, and shook it. Then he closed his two hands over the lock, worked at it a few seconds, and presto! it opened.

The barker stared in blank amazement. Then he scowled. He had not expected anyone to open the padlock.

"Gimme my money," demanded the stranger who had won the contest.