Chapter III: Part 3

"But you promised me first option on it!" Mr. Johnson protested. "If necessary, I can wait for the demonstration tomorrow night, though it will greatly inconvenience me."

"Tomorrow at eight o'clock," the professor nodded. "If you should care to put up a small sum of money as a guarantee of your intentions, I promise to make no final deal with the Navy until after that time."

"Why, yes," Mr. Johnson agreed, taking out his check book. "Any amount you say."

Feeling themselves no longer welcome by the Bettenridges, Penny and Louise slipped quietly away. As they climbed the hill they could hear the professor and Mr. Johnson discussing the amount to be paid.

"It's a graft, if you ask me," Penny declared. "Poor Mr. Johnson seems hypnotized."

"I wish we could see that test tomorrow night!"

"So do I. In fact, I'd be willing to bet the machine won't work."

"What makes you think so?"

"Just my doubting nature, I suppose. No, there's more to it than that, Lou. Didn't you notice how startled the Bettenridges were when their star customer appeared?"

"They did look a bit upset."

"And the professor refused to give a demonstration tonight, although obviously it would have been to his advantage."

"He explained he had an engagement with Navy men."

"Which I suspect was all a made-up story. No, Lou, there must be another reason why the professor was unwilling to give the demonstration. He probably knows his machine won't work."

"You're convinced he's a fraud."

"Yes, I am," Penny said. "Furthermore, I believe he knows what became of Salt's camera."

"We can't prove anything."

"No, but if he would steal a camera he might also take to swindle in a big way."

"There's nothing we can do unless we want to report him to the police."

"I have a little idea," Penny confessed. "As soon as we reach Riverview I propose to check the Gables Hotel and learn if any Navy men have registered there. By talking to them, we may get at the truth."

CHAPTER
12
_THE PROFESSOR'S HELPER_

Climbing the hill, Penny and Louise sought their parked car. The day had been an interesting one, replete with surprises, and yet another surprise was in store.

As they were ready to drive away, a man came slowly down the road, cut across the Leonard yard and vanished down a path which led toward Blue Hole Lake.

"See that fellow!" Penny exclaimed.

"Why, yes," agreed Louise, surprised by her chum's tense manner. "What about him?"

"I'm sure he's Webb!"

"Webb?"

"The man who was pushed off the _Snark_ and who stole Ben's watch!"

"What would he be doing here?"

"That's exactly what I want to learn! I'd like to get Ben's watch back for him!" Quickly Penny pushed open the car door and jumped out.

"What are you going to do, Penny?" Louise asked anxiously.

"Follow that man and learn for certain who he is!"

"But it's late," Louise protested. "Besides, he looks like an unpleasant sort of individual."

Penny paid no heed, but started off in pursuit of the stranger. He had already disappeared among the trees and was well on his way toward the lake. Not wishing to be deserted, Louise quickly followed her chum.

"He's going to the professor's shack!" Penny observed a moment later.

"Perhaps he is another prospective buyer of the secret ray machine," Louise speculated. "Business seems to be rushing today."

Penny was not convinced. "I'm sure it is Webb," she declared. "If we can force him to admit his identity, we may get Ben's watch back."

Not wishing to attract attention, the girls paused behind a large rock on the hillside. From there they could watch the man without being seen.

He walked directly to the shack and tapped on the door. In a moment it was opened by the professor, who looked anything but pleased to see the new arrival. Closing the door behind him as if fearful that Mr. Johnson would hear, he stepped out of doors.

The girls were too far away to overhear the conversation, but they saw the two men talk earnestly together for a moment. Then the man they believed to be Webb, walked on down the hill toward the lake's edge. Professor Bettenridge reentered the shack.

"Now what?" inquired Louise, straightening up from a cramped position behind the rock.

"Let's follow Webb. I have a hunch he may be the assistant Professor Bettenridge told Mr. Johnson about."

"But the man wasn't expected here until tomorrow."

"Which may or may not have been true, Lou. There's more to this deal than meets the eye. Let's see what we can learn."

Already the man had disappeared from view, so the girls walked swiftly after him. Reaching the lake's edge, they saw him striding along the sandy beach. Apparently he had no suspicion that he was being trailed, for he did not glance backward.

Presently the girls noticed another shack which had been erected in a clump of trees a few yards back from the beach. It was much smaller than the other little house, a mere box-like structure with a flat, low roof.

Walking directly toward it, the man unfastened a padlock and went inside. He closed the door behind him.

"Now what is he doing in there?" Penny fretted, as minutes elapsed and the man remained inside the building. "Listen!"

Both girls could hear a peculiar grinding sound as if from machinery turning inside the shack. The building was windowless, so it was impossible to see what was going on.

"This is maddening!" Penny muttered with increasing impatience. "I wonder--?" She broke off, and gazed thoughtfully at the flat roof of the shack.

"Lou, how is that building lighted?" she demanded.

"From here it looks as if there might be double panels of glass in the roof--a make-shift skylight."

"Lou, if we could get up there, we might be able to see what is going on!"

"And get caught too!"

"Not if we're careful. We can climb that tree which brushes against it, and perhaps see from there."

"What if we should be caught?"

"We'll decide that part when the time comes," Penny chuckled. "This should be fun."

Circling the shack, they climbed into the low-hanging boughs of a giant, scraggly maple tree. Inch by inch lest they make a sound which would betray them, they climbed out on the heavy branches.

"Penny, we're taking an awful chance," her chum murmured nervously. "If that man should look up--"

"He won't," Penny whispered confidently. "He's too busy with whatever he's doing."

Lying flat on the branch, she could look directly through the glass. In the room below she saw at least four large, oval-shaped mines without detonators, made of steel.

Evidently the man had finished whatever work had brought him to the shack, for he laid aside a tool, and then went out the door, carefully locking it behind him again.

"We were too late," Penny whispered in disgust after the man was a safe distance down the beach. "I wish I knew why he came here! One thing is certain, he's mixed up with Professor Bettenridge on this secret ray invention."

"Do you still believe the man is the one who was pushed off the _Snark_?"

"Yes, I do, and that part we can learn!" Realizing that much valuable time was being wasted, Penny slid down from the tree, snagging a stocking in the process. She helped Louise to reach the ground.

"What's the plan now?" her chum asked.

"Webb evidently is returning either to Professor Bettenridge's shack or to town. Let's overtake him and I'll ask a few questions. After helping fish him out of the river, I certainly have the right."

The man walked directly toward the shack which contained the secret ray apparatus, but when he drew close, paused and whistled twice as if in signal. No response came from within the cabin. Seemingly the man expected none, for he turned and selected a trail which led toward the road.

At that moment, the shack door opened. Professor Bettenridge, his wife, and Mr. Johnson came out together, chatting pleasantly. Without paying the slightest heed to Webb, they walked toward the farmhouse.

"What do you make of all that?" Louise asked in perplexity.

"I'm not sure," Penny admitted. "But I have a suspicion the professor doesn't want Mr. Johnson to know Webb is here today. He might insist on a test of the secret ray machine."

"Why all the mystery? Professor Bettenridge certainly can't expect to sell the invention unless he can give a successful demonstration."

"I suspect that may be the point, Lou. Things aren't properly set for a successful test today. Tomorrow night may be a different story."

"But if the machine is as good as the professor claims, it should explode mines as well one time as another."

"It should," Penny agreed, "but whether or not it does, is a horse of a different color. My guess is that the professor is a fraud, and that Webb helps him in his scheme."

The man believed to be Webb walked so rapidly that the girls realized they would lose sight of him unless they hastened on. Cutting across a field, they were able to get ahead of him.

"Yes, it's Webb," Penny whispered as they waited for the man to approach. "I'm certain."

Not until he was quite close did the man see the girls. Momentarily startled at recognizing Penny, he ignored her, and would have passed without a word.

"Webb!" she exclaimed. "Don't you remember me?"

The man halted, gazing at her with ice-cold, unfriendly eyes.

"Webb ain't my name," he said gruffly. "I never saw you before."

"You may not remember. I helped pull you out of the river after you had fallen from the deck of the _Snark_."

"Are you coo-coo?" the man demanded. "I don't know what you're talking about."

"I think you do," Penny said, losing patience. "You stayed with Ben Bartell at his shack by the river. For saving your life, you repaid him by stealing his watch!"

"Say, young lady, better be careful what you're sayin'!" the man snapped. "No one can accuse me of being a thief!"

"I want Ben's watch."

The man started on down the road, but Louise and Penny stood their ground, blocking his way.

"I want the watch!" Penny repeated firmly. "If you won't give it up, I'll report you to the police."

"Oh, you will, eh?" The man whirled toward her, his face convulsed with anger. "You'll get no watch from me, but here's something to teach you to mind your own business!"

With a cruel laugh, he pushed her so hard that she sprawled backwards into the ditch.

CHAPTER
13
_BEHIND OFFICE DOORS_

"Are you hurt, Penny?" Rushing to her chum, Louise helped her out of the ditch where she had fallen.

"No!" Angrily, Penny brushed dust from her slacks. "But I'm as mad as a hornet! If that man thinks he can push me around--"

Already Webb was well down the road, walking at a leisurely but arrogant pace.

"Forget it, forget it," Louise soothed. "We'd get no place picking a quarrel with a man like that. Anyway, you more or less accused him of thievery."

"And a thief is exactly what he is!" Penny retorted. "There isn't a doubt in my mind that he's the one who stole Ben's watch!"

"Then the thing for us to do is report him to the police. We'll get nowhere talking to him ourselves."

"We'll stop in town--I think the place is called Newhall--and notify the sheriff," Penny decided. "I certainly shall ask for the man's arrest."

Returning to the car, she turned it around, and they drove toward the town, less than a half mile away. Soon they approached Webb who was walking at the side of the pavement. Deliberately, he ignored them as they passed.

At Newhall, the girls found the sheriff, and rather excitedly, poured out their story. Although the official took a few notes, he seemed somewhat bored by it all.

"You don't know the last name of the man," he recited. "You think he may be employed by Professor Bettenridge, but you are not sure. You believe he may be a thief, but you are not positive of that either."

"One thing I am sure of!" Penny exclaimed. "He pushed me into a ditch. So at least he's guilty of that!"

"Are you willing to sign charges and appear against the man?"

"You mean I would have to come back here later on?"

"Certainly."

Penny's enthusiasm waned. "Maybe I couldn't get here," she said, thinking of her newspaper work. "Oh, well, let it go."

"I'll keep an eye on the man anyhow," the sheriff promised. "Think you have the situation sized up wrong though. We've already investigated Professor Bettenridge. He has fine credentials, and his invention seems to have merit."

"You believe it actually will explode mines?" Penny asked incredulously.

"I saw it done. Fact is, Professor Bettenridge invited me to the first demonstration he gave at the lake."

"What happened?" Louise questioned eagerly.

"A mine was dumped into the lake. Then the professor exploded it with his machine. I didn't understand how it was done, but I saw the flames shoot up when it went off. It was the real thing."

Decidedly let-down, Penny and Louise took leave of the sheriff and drove to Riverview. But as they passed through the downtown section, Penny suddenly stopped in front of the Gables Hotel.

"I suppose I'm silly," she acknowledged, "but I still doubt the honesty of Professor Bettenridge. Just for the fun of it, I intend to run in here and learn if those Navy officials are registered."

Leaving her chum in the car, Penny was gone nearly fifteen minutes. When she returned, her face had taken on animation, so Louise knew she had interesting news.

"Just as I thought!" Penny exclaimed, sliding behind the steering wheel. "Not a Navy officer registered in the hotel, and none expected! So how could Professor Bettenridge have an appointment here tonight? He merely told Mr. Johnson that to impress him."

"It does look that way. Still, it's possible the officers might have registered at another hotel."

"Possible but hardly probable. Lou, I believe Professor Bettenridge is a crook. I wish we could witness that demonstration of his tomorrow night!"

"I'll never be able to go," Louise said regretfully. "I'm playing in a recital--worse luck."

"I might get Salt to ride over with me," Penny thought aloud. "Well, we'll see."

The following morning she took time from her work to seek the photographer. He was in the darkroom, but the door was open. As she stepped inside, he whirled around, his face startled.

"Oh, it's you!" he chuckled in relief.

"Why, Salt!" Penny teased. "You acted as if you thought I might be a holdup man. Why so jumpy?"

"Was I?" the photographer asked, his tone queer.

"You certainly were. Anything wrong?"

"This place was entered again last night," Salt said reluctantly. "I can't figure it out."

"Anything taken?"

"Not a thing so far as I can discover. That's the strange part of it. But the films were disturbed, as if someone had searched through them."

"How did the person get in?"

"Apparently through the skylight. It was ordered locked, but it got hot in here yesterday. One of the boys opened it up, and then forgot to snap the lock."

"Did you search the roof?"

"Yes, we found footprints leading to a hall window of the next building. That was as far as they could be traced."

"Do you suppose it could be anyone from the adjoining building, Salt?"

"Not necessarily. The person may have entered it from the street. We know he stepped out onto the roof from the hall window rather than from one of the office rooms."

Before returning to the newsroom, Penny told Salt about yesterday's adventure in the country.

"I sure would like a chance to go there with you tonight," he declared promptly. "Maybe we can get my camera back, even if those birds deny having seen it."

The morning passed slowly, and Penny found it difficult to keep her mind on her work. Elda, however, no longer bothered her. With more important problems to worry about, Penny was not the least bit wounded by the little slurring remarks the girl made.

At noon she lunched on a sandwich and chocolate at a corner drugstore close to the _Star_ building. With half an hour to spend, she suddenly was struck by an idea.

"Why don't I talk to Jason Cordell, the _Mirror_ editor, about Ben?" she thought. "Perhaps their difficulties are based on misunderstanding."

Crossing the street to the _Mirror_ building, she found Mr. Cordell's office on the third floor. There, a secretary asked her to wait a few minutes.

Apparently an argument was in progress within the inner room, for she heard angry voices. Then a door slammed. Presently, Penny was told that she might go in.

Mr. Cordell sat at his desk, a scowl on his face. He was busy writing and barely glanced up as she entered. Finally he looked straight at her, demanding: "Well?" in a tone which sapped Penny's courage.

She wished she might retreat, but it now was too late.

"I--I am Miss Parker," she stammered. "My father is publisher of the _Star_."

"Oh, yes, yes indeed," the editor now became more friendly, and Penny took heart.

"I came to talk to you about one of your former employes--Ben Bartell."

A mask-like expression came over Mr. Cordell's face. He waited for Penny to continue.

"You discharged Ben, I believe. He's had a very hard time ever since."

"Indeed? Is he a friend of yours?"

"In a way. I feel sorry for him and I want to find newspaper work for him."

"Then why doesn't your father give him a job on the _Star_?"

Penny was prepared for the question. "I think my father would if he were assured that Ben had done nothing so very dishonorable. That's why I came to you. Why was he discharged?"

"Unfortunately, I can't reply to that question. Nor can I assure you that Ben was discharged on a trivial offense. The opposite is true."

"But what did he do?"

Mr. Cordell arose. "I am sorry, I can't discuss it, Miss Parker. If you will excuse me for saying so, I think the matter really is not your concern. My advice would be to leave Ben Bartell entirely alone. He sent you here, I suppose?"

"Indeed, he didn't."

"Where is Ben now?"

"Living in a shack on the waterfront. Because you blacklisted him, he has been unable to get a newspaper job anywhere."

Mr. Cordell's smile was hard and triumphant. Penny knew then that she had made a grave error in thinking she might appeal to the man's sympathies. Obviously, he was highly pleased to learn of Ben's difficulties.

"I am sorry I can't help you," the editor said coldly. "Do drop in again sometime."

He opened the door for her, a pointed hint that she was to go.

As she stepped out into the outer waiting room, a man who evidently expected to see the editor, arose. He had entered the outer office only a few minutes before, and this was the first time that Penny had seen him. Upon recognizing him, she stopped short, for it was Webb.

"You can go in now, Mr. Nelson," the secretary told Webb.

Bestowing a sneering smile upon her, he entered the private office.

Then the door closed.

CHAPTER
14
_A NOTE FROM BEN_

After Webb had gone into Mr. Cordell's office, Penny debated her next action. Could Webb and Cordell be friends? Or was this merely a business call? In any case, the two men were obviously of such different type and personality that she failed to understand what basis there might be for a friendship.

Deciding she could accomplish nothing by waiting and questioning Mr. Cordell, she left the office. As she passed down the corridor, an open window at its far end, drew her attention.

Pausing for an instant, she glanced out upon the rooftop of the _Riverview Star_ building. The tin flooring, only a few feet below the level of the sill, easily could be reached by anyone climbing through the window.

Tempted to take a short cut to the office, Penny impulsively stepped through the opening. From the rooftop she could see the city spread out below in rigid pattern, and to the eastward, the winding river.

Crossing the dusty floor to the skylight above the _Star_ photography room, Penny peered curiously down. No one was visible below.

"I wonder if a person really could get through that skylight," she speculated. "It would be quite a feat, but I believe it could be done."

A star athlete in high school, Penny felt a challenge. Giving no thought to her clothes, she squeezed through the narrow opening and snagged her sweater. As she freed herself, she noticed a tiny bit of blue cloth that had impaled itself on the nail.

The cloth was not from Penny's garments, and looked as if it might have been torn from a man's wool suit. Freeing it from the nail, she slipped it into her pocket for later examination.

Now, with her feet dangling into space, she considered how she was to get down into the room below. No longer was it possible to swing from the opening to the top of a filing cabinet, for Salt had carefully moved the heavy case to the far side of the room.

Seizing the skylight chain, Penny swung downward. The tiny brass rings cut into her hands and half-way down, she was forced to let go, dropping to the floor with a loud thump.

From the inner photography room came a terrified scream. Elda Hunt, her face white with fear, appeared in the doorway.

"You!" she exclaimed, recovering from the shock of Penny's unexpected entry.

"Now take it easy, Elda," Penny advised, brushing dirt from her sweater. "I was only experimenting."

"Experimenting!"

"I wanted to see if it would be possible for a person to get into this room through the skylight. It is possible!"

"You don't say!" Elda commented sarcastically. "I'll bet you were the one who pulled that stunt in the first place!"

"How ridiculous!" Penny was irritated. Not wishing to discuss the matter, she turned and walked out of the photography room.

In the corridor she met Salt Sommers who stopped her to ask when they were to visit Professor Bettenridge in the country.

"Eight o'clock tonight, if you're willing to go," Penny said eagerly. "I very much want to see the professor demonstrate his ray machine for Mr. Johnson."

"And I want to find out what became of my camera," Salt added grimly. "Is it a date?"

Penny nodded.

"Then suppose we start right after dinner. Can you meet me here at seven o'clock?"

"Let's make it a little earlier," Penny suggested. "I have a hunch that by getting there before the start of the demonstration we may learn more."

"Okay," agreed Salt. "Make it six-thirty."

Having over-stayed her lunch hour, Penny quickly washed her grimy hands and returned to her desk. As she sat down at the typewriter, she noticed a sealed letter thrust behind the roller. Addressed to her, the writing was in a bold scrawl she did not recognize.

Curiously, she scanned the message. It was written on cheap tablet paper and had been signed with Ben Bartell's name.

"See me if you can," was all it said. "I have a little information about the _Snark_."

Tucking the note into her pocketbook, Penny began to plan how she could visit Ben that day. She would not be off until five o'clock, and she had promised to meet Salt at six-thirty. If she were to get any dinner and see Ben at the waterfront, it would mean fast stepping.

Only by an effort of will could Penny keep her mind on the work before her. There were rewrites to do, and an interesting feature. At four-thirty with two stories yet to be done, she became panicky that she could not finish on time. But by really digging in, she completed the stories exactly on the dot of five, and with a tired sigh of relief, dropped them into Editor DeWitt's wire copy basket.

"You're just like a trained race horse, Penny," he said jokingly. "But your work is okay. You're improving."

Penny brightened at the praise, for Editor DeWitt was not given to complimentary words as a rule. Hurriedly washing carbon paper stains from her hands, she caught a bus which took her within a block of Ben's shack.

Smoke curled from the chimney, and as she thumped on the sagging door, she detected the odor of cooking bacon.

"Come in, come in!" Ben greeted her heartily. "You're just in time to share my supper. You got my note?"

"Yes, I did, Ben. What's up?"

Without answering, the former reporter stepped aside for her to enter. The room was much cleaner than when Penny last had visited it. Ben looked better too. Although his clothes remained unpressed, his hair had been cut, and there was a brightness to his eyes which she instantly noted.

"You've found work?" she surmised.

"Odd jobs," Ben answered briefly. "After talking to you I made up my mind I'd better snap out of it. If I can't find newspaper work, I'll try something else."

"I was thinking--" Penny sat down in a rickety chair, "--couldn't you do free lance work? Write stories for newspapers out of town?"

"Without a typewriter? I put mine in hock months ago, and it finally was sold for charges."

"I have a typewriter at home, Ben. I'll lend it to you."

Ben's face brightened, but he hesitated. "I've sure been lost without a machine," he declared. "But I hate to take yours. You know what happened to my watch. This shack isn't safe. Anyone might come in here and steal it."

"It's only an old typewriter, Ben. I'm willing to take a chance. I'll see that you get the machine within a day or so."

The former reporter stepped to the stove to turn the bacon. He kept his face averted as he said: "Penny, you've been a real friend--the only one. That day when you met me--well, I didn't give a darn. I was only one step from walking off a dock."

"Don't say such things, Ben!" Penny warned. "You've had a run of hard luck, but it's changing now. Suppose you tell me what you learned about the _Snark_."

"Nothing too startling, so don't get your hopes up," Ben grinned.

He set out two cracked plates on the battered table, two cups for coffee, and then dished up the bacon and a few fried potatoes. It was a meagre supper, but not for the world would Penny have offended Ben by refusing to share it.

"Now tell me about the _Snark_," she urged again, as Ben poured the coffee.

"I've been watching the boat at night, Penny. Queer things go on there."

"We suspected that after seeing Webb pitched overboard."

"I've seen a lot of men come and go from that vessel," Ben resumed. "It's a cinch they couldn't all be employed on her, because the _Snark_ has been out of service for months."

"What do you make of it?"

"Oh, the _Snark_ is being used as a meeting place--that's obvious. Just for the fun of it, I sneaked aboard last night."

"What did you learn, Ben?"

"The men were having a confab in one of the cabins. I couldn't hear much, but enough to gather that they are afraid Webb will talk to the police."

"About what, Ben?"

"Didn't learn that part. I aim to keep tab on the place for a while."

Penny told of seeing Webb that afternoon and also of his association with Professor Bettenridge.

"A secret ray machine, my eye!" Ben exploded. "You may be sure it's a fake if Webb has anything to do with it! Penny, this is no business for you to be mixed up in. Webb is a dock rat and as surly an egg as I ever met. You ought to give him a wide berth."

"I'll certainly be careful," Penny promised, arising. "Sorry to leave you with the dishes, Ben, but I must run or I'll be late for another appointment."

She really hated to go, for she saw that her companionship had made the young man more cheerful. Ben walked with her through the waterfront district, and then reluctantly said goodbye.

Hastening along the shadowy street, Penny noticed the large electric sign on top of the Gables Hotel.

Impulsively, she stopped at the hotel.

"That Navy official Professor Bettenridge spoke of may have arrived," she thought. "Just to make certain, I'll inquire again."

CHAPTER
15
_THE DEMONSTRATION_

Penny was due to meet Salt Sommers in ten minutes, but if she were late, she knew he would not leave without her.

Entering the crowded hotel, she waited her turn at the desk and then inquired if any Navy officers had registered.

"Not to my knowledge," the clerk replied, consulting the register. "No, we've not had a Navy man in for at least a week."

"Any Army officers?"

"The last was a sergeant who checked out two weeks ago. Most of our guests rent on a monthly basis. We have only a few rooms for transient guests."

"Can you tell me if a Professor Bettenridge has called here in the last few days?"

"Not while I've been at the desk."

The information convinced Penny she had not misjudged the professor. She now was satisfied he never had arranged with Navy officers to inspect his ray machine. Instead, he had misinformed Mr. Johnson, no doubt hoping to impress him that others were interested in the invention.

Quickly leaving the hotel, Penny hastened on to the news office. As she passed near the loading platform, Salt hailed her from a car parked there.

"Here I am," he called.

Penny slid into the front seat beside him, apologizing for being late.

"That's okay," returned Salt, shifting into gear. "But we haven't much time unless we hurry. You know the way, don't you?"

"I do by daylight. And I think I can find the farmhouse, even if it should get dark before we reach there."

Salt was a fast and very skillful driver. He chose the less frequented streets and soon they were in the open. They made excellent time, reaching their destination just as it began to grow dark.

"How shall we explain to the professor?" Penny inquired dubiously as the photographer parked the car under an oak tree along the highway. "He may think it strange that I returned."

"Let him," said Salt, unconcerned. "I'm here to get my camera."

"Don't go at him too hard," Penny pleaded. "After all, there is a chance I was mistaken about the license number. In my excitement the night of the explosion, I may have remembered a wrong figure."

"That's so," Salt acknowledged gloomily. "Well, we'll see."

"Why not pretend we're here to get a feature story for the _Star_?" Penny suggested impulsively. "That way, I could ask him all the questions I like about the secret ray machine."

"Any way you want to do it," Salt agreed amiably.

He locked the car and they walked to the farmhouse. Learning that the professor and his wife were at the lake, they trudged down the lane.

"Wait!" Penny suddenly warned in a whisper.

Clutching Salt's arm, she drew him into the shadow of a tree. At first he could not understand the need for caution. Then as Penny pointed, he saw a hunched figure with a lighted lantern, walking along the lake shore away from the cabin where Professor Bettenridge's ray machine was kept.

"There goes Webb now!" Penny whispered. "He's evidently going to the shack where the mines are stored."

"What's he carrying?" Salt inquired.

Although too far away to see plainly, they thought that he had a small satchel tucked under his arm. As he drew closer they discerned that it was leather, and apparently used as a container for a long cylinder-shaped object.

Passing a short distance away, the man did not see Salt or Penny. They watched until they saw the red glow of his lantern vanish over a hillock.

"That's the foot-path to the shack where the mines are stored," Penny commented. "I wonder what's inside the satchel?"

"Shall we try to find out?"

"Let's talk to Professor Bettenridge first," Penny proposed, going down the lane.

The door of the cabin stood slightly ajar. Inside the lighted room were the professor, his wife, Mr. Johnson, and several other persons Penny had never seen before. However, she took them to be town residents who had heard of the test and were eager to see it.

"Well, professor," they heard Mr. Johnson say jovially. "We're all here, so why not go ahead? Show us what the machine will do."

"All in good time, all in good time," the professor rejoined. "You must give my assistant an opportunity to drop the mine into the lake. He will signal us by lantern when he is ready."

Penny tapped on the door. The professor whirled around, decidedly startled. Then, observing Salt and Penny, he abruptly came over to speak to them.

"Well?" he asked in a tone which was not friendly.

"We came to see the demonstration," Penny said brightly.

"Glad to have you," the professor replied, though without cordiality.

"We want to write a feature story about your machine too," Penny continued. "For the newspaper."

The request displeased the professor. Scowling, he said curtly:

"I am sorry, but there must be no publicity at this time--orders of the Navy, you know."

"The Navy is interested in buying your machine?" Penny asked, hoping to lead him on.

"The deal is concluded except for my signature," the professor said, darting a quick glance at Mr. Johnson. "I should have signed at once, but I promised Mr. Johnson first chance to buy the machine."

"I suppose the Navy men are in town now?" Penny inquired.

"In Riverview."

"At the Gables Hotel?" Penny pursued the subject.

The professor looked at her sharply, for the first time suspecting that she was inducing him to reveal far too much.

Without answering, he turned his back, and began to talk to Mr. Johnson about technical details of the machine.

"I am convinced it is a wonderful invention," the latter declared. "But before I invest $200,000, I must be absolutely certain that it will do everything you claim."

"You shall not be disappointed," reassured the professor. "Only be patient for a few minutes, and you will witness a demonstration that will convince you beyond a shadow of a doubt."

Ignored by the professor and his wife, Penny and Salt did not enter the cabin. Instead, they walked a short distance away to discuss their next move.

"The demonstration won't start for a few minutes," the photographer said. "Suppose we ankle down to the lake and find out what Webb is doing."

Proceeding down the path which led around the lake shore, they soon sighted the man's glowing lantern. He had set it down on the ground while he trundled out one of the heavy mines from the shack. As they watched from a distance, he loaded it into a boat, picked up the lantern, and slowly rowed out into the lake.

"Apparently he's going to drop it overboard for the test," Salt said. "While he's out there, let's take a look in the shack."

He tried the door. It was locked.

"I don't know how it's done, but I'm sure those mines are doctored in some way," Penny declared. "Louise and I saw Webb working on one when we were here yesterday, but what he did I couldn't guess."

"We'll learn nothing here," Salt said. "Let's go back to the cabin and see how the professor pulls off the demonstration. Apparently he has Mr. Johnson two-thirds convinced already."

"Whatever you do, don't get into an argument with the professor about your camera until after the test," Penny pleaded as they started up the slope again. "I want to watch the demonstration. If you accuse him of deliberately keeping the camera, he may throw us out."

"Okay, I'll wait," Salt promised.

Reaching the cabin, the pair became instantly aware of a tenseness in the attitude of the professor and his wife. Although they did not tell the newcomers they were unwelcome, it was evident by their expressions that they distrusted Penny and Salt.

Professor Bettenridge stood behind his machine, explaining its many parts to the awed spectators. Penny could make nothing of the technical jargon.

"The demonstration will soon start," the professor declared, looking at his watch. "I will turn on the motors now, as they must heat for several minutes."

He turned several switches and the room was filled with a low humming sound. Two tiny lights buried deep in the complicated mechanism began to glow a cherry red. The professor bent low over the machine, frowning thoughtfully. He adjusted three of the concave mirrors, and switched on another motor.

Despite a dubious attitude, Penny found herself becoming deeply impressed. Was it possible, she wondered, that she had misjudged the professor and his machine? She dismissed the thought. The mine never would explode unless it had been tampered with--she was certain of that.

"Watch closely now," the professor directed. "At any moment my assistant will signal with his lantern that he has dropped the mine and is safely away from the area."

The professor's wife had gone to the doorway. Tensely she watched the lake. Minutes passed. Then from out on the water, there came a moving circle of red--the signal from Webb.

"Now!" exclaimed the professor's wife.

Everyone in the little cabin held his breath. Dramatically, Professor Bettenridge took a metal tuning fork and struck it sharply against the crystal ball in the center of his machine.

"It will take a moment for the sound to reach the lake," he said softly. "But only a moment. Watch closely."

All persons in the room crowded to the door and the windows. Suddenly a huge burst of flame appeared on the lake, fanning out on the surface of the water. A moment later came the dull boom of a terrific explosion.

CHAPTER
16
_SUSPICION_

Everyone who witnessed the spectacular demonstration was awed by the sight of the flames rising above the lake. As they died away, Professor Bettenridge, strutting a bit, walked back to his machine and covered it with the canvas hood.

"Now are you satisfied?" he inquired triumphantly. "Is there anyone here who doubts the remarkable possibilities of my invention?"

"It was a fine demonstration! Magnificent!" approved Mr. Johnson, fairly beside himself with excitement. "I am convinced of the machine's worth and if we can agree upon terms I will write you a check tonight."

Professor Bettenridge's expression did not change, but the brief glance he flashed his wife was not lost upon Penny or Salt.

"You understand, of course," he said smoothly, "that the Navy probably will insist upon ultimate purchase of the machine even if I relinquish ownership?"

"Certainly," agreed Mr. Johnson. "I should expect to make such a sale. The machine would have no practical use except in warfare."

Penny was tempted to ask the man if he considered it patriotic to try to obtain control of a machine in the hope of selling it to the government at a high profit to himself. But she wisely remained silent.

Salt, however, had a few pointed remarks to offer.

"How come," he observed, "that if this invention is so remarkable, the Navy hasn't already snapped it up?"

Professor Bettenridge froze him with a glance. "Young man," he said cuttingly, "you evidently do not understand how government business is conducted. Negotiations take months to complete. My wife and I need cash, so for that reason, we are willing to sell the machine quickly."

"Yesterday I understood you to say that Navy men were ready to complete the deal," Penny interposed innocently. "Did they change their minds?"

"Certainly not!" Professor Bettenridge's dark eyes flashed, and only by great effort did he maintain control of his temper. "You understand that while their recommendation would eventually be acted upon, a sale still would take many months to complete."

"Will your machine explode mines on land as well as in the water?" Salt inquired.

"Of course!"

"Then why not give us a land demonstration?"

"Us!" the professor mocked, his patience at an end. "Young man, you were not invited here, and I might add that your presence irritates me! Are you in any way associated with Mr. Johnson?"

"I am not."

"Then kindly do not inject yourself into our negotiations."

"The young man raises an interesting point," Mr. Johnson interposed, frowning thoughtfully. "Perhaps we should have a land demonstration before I pay over the money."

"So you doubt my honesty?" the professor demanded.

"Not at all. It's only that I must be very careful before I purchase such an expensive machine. I must satisfy myself that it will do everything you claim for it."

"You have just witnessed a successful demonstration. What more do you ask?"

"A successful water test," Salt remarked softly, "does not necessarily mean a successful land test."

"I think we should have a land test," Mr. Johnson decided. "If you convince me that the machine will work equally well under such circumstances, I will write the check instantly."

"A land test is impossible," the professor said stiffly.

"But why?" inquired Mr. Johnson.

"The dangers are too great. Windows would be smashed for many miles around. Authorities would not permit such a test. Only with the greater difficulty did I obtain permission to discharge the mines under water."

"I had not thought of that," Mr. Johnson acknowledged. He hesitated, and it was evident that in another moment he would decide to purchase the machine without further tests.

"Mr. Johnson, I suppose you have witnessed tests made with your own mines," Penny interposed. "Or have they all been made with those supplied by the professor?"

The remark infuriated Mr. and Mrs. Bettenridge, as she had expected it would.

"You and this young man are trying to discredit my machine!" he exclaimed wrathfully. "Please leave."

"Why, certainly," agreed Penny, but made no move to depart.

Seeds of suspicion already had been implanted in Mr. Johnson's mind.

"The young lady is right," he said. "I should request a test on a mine which I provide myself."

"Ridiculous!" snapped the professor. "The machine will work equally well on any mine."

"Then surely you should not object to one further test?"

"The delay is unnecessary."

"I am certain I can provide a mine within two days," insisted Mr. Johnson. "Suppose we set the next test for Thursday night at this same hour?"

Thus trapped, Professor Bettenridge could not refuse without losing the sale. Scowling, he gave in.

"Very well. But this will be the final demonstration. If you are not satisfied Thursday night, the deal is off."

"Agreed," said Mr. Johnson.

Bowing to the Bettenridges, he departed. Others who had witnessed the demonstration began to melt away. Only Salt and Penny remained.

Professor Bettenridge closed the door so that the conversation would not be overheard. Then he turned angrily to the pair.

"Now what's your little game?" he demanded. "You deliberately tried to queer my sale? Why?"

"Mr. Johnson seems like such an innocent little rabbit, maybe we thought he ought to be protected," Salt drawled.

"Protected! Why, he's being given the opportunity of a lifetime! How much is it worth to you to keep out of my affairs?"

"Not a cent," Salt retorted. "We don't want any part of your deal. But there's something I did come here for--my camera."

"I've already told the young lady I know nothing about it. If you were stupid enough to throw it into a passing automobile, then you deserve to lose it. Now get out!"

Salt was tempted to argue the matter, but Penny took his arm, pulling him toward the door. The professor slammed it hard behind them as they went out into the night.

"That fellow is a crook!" Salt exploded. "I'll bet a cookie he has my camera too!"

"Well, we can't prove it," Penny sighed. "After all, we did act in a high-handed way. We may have queered his sale to Mr. Johnson."

"A good thing if we have."

"But we have no proof the machine is a fake. With our own eyes we saw the mine explode. Of course, we think Webb tampered with it in some fashion, but we're not certain of that either."

"The proof of the pudding will come Thursday night when and if the old boy explodes Mr. Johnson's mine."

"He's just clever enough to do it, too," Penny said gloomily.

The couple had walked only a short distance up the lane when they were startled to hear a shrill whistle in the darkness. It came from the beach.

Halting, they waited. In a moment the sound was repeated. Then to their surprise, came an answering whistle from inside Professor Bettenridge's cabin.

"That must be Webb," Salt whispered, observing a shadowy form approaching. "The whistle evidently is a signal to make certain the coast is clear."

As they watched, the hunched figure emerged from the darkness, was silhouetted momentarily in the light which came from the cabin, then disappeared inside.

"I wish we knew what they were talking about in there," Penny said. "It might clear up some of the mystery."

"Why not see what we can learn?" proposed Salt. "It's safe enough."

Taking care to walk softly, the pair stole back to the cabin. Crouching by the window, they could hear a low murmur of voices inside. At first it was difficult to catch the trend of the conversation, but gradually Professor Bettenridge's voice grew louder.

"I don't like it any better than you do," Salt and Penny heard him say, "but that's the way it is. If we're to finish the deal, we've got to explode one of Johnson's mines Thursday night. The question is, can we do it?"

"Depends on the type of mine," Webb replied gruffly. "How soon can we have it ahead of the test?"

"I'll insist that he deliver it here at least by afternoon. Will that give you time enough?"

"Sure, it won't take more than a half hour to fix 'er for the test, providing it can be done. But I ain't makin' no promises until I see the mine."

"It's a chance we have to take," Professor Bettenridge said. "The deal would have gone through tonight if it hadn't been for a couple of young newspaper fools who came nosing around here. They may make us trouble Thursday night too."

"I ain't aimin' to get mixed with the police," Webb said uneasily. "If this deal don't go through Thursday night, I'm quitting. We're in a mighty risky business."

"But we stand to make at least $200,000," the professor reminded him. "You'll get a third cut. If Johnson holds off Thursday night, I'll drop to $100,000. The thing we've got to do is to pull off that test okay and clear out."

Penny and Salt had heard enough to be certain that the men with whom they were dealing were crooks of the first rank. Slipping noiselessly away, they trudged to the car.

"Now what do we do?" Penny questioned. "Notify the police?"

"We could," Salt debated, "but so far, it's only our word against Professor Bettenridge's. He'd probably convince the police he was only a crack-pot inventor who thought he had a wonderful machine. They might let him go."

"Any other ideas?"

"A slick trick would be to fix that mine so it won't explode. That automatically would cause complications and probably delay the deal with Mr. Johnson."

"Just how do you propose to fix Mr. Johnson's mine?" Penny inquired. "It would take some doing."

"The mines are all kept in that shack on the beach?"

"Yes, Louise and I saw Webb working on one of them there. Evidently it was the one the professor exploded tonight."

"He must have doctored it in some special way. Probably an untampered mine won't explode."

"He'll fix Mr. Johnson's mine the same way, and then the test will appear successful."

Salt nodded gloomily. He was lost in thought for several minutes, and then he grinned.

"Maybe I have an idea!"

"What is it, Salt?"

The photographer switched on the car ignition. "Wait until Thursday night," he replied. "Can you get away from the office early?"

"Well, I really shouldn't--"

"I'll take care of that part," Salt said briskly. "Just sit tight, Penny. You and I will have some fun out of this affair yet, and maybe we'll save Mr. Johnson a tidy sum of money."

CHAPTER
17
_MAJOR BRYAN_

It was nearly midnight by the time Penny reached home. Mrs. Weems had gone to bed, but a light still burned in the study where Mr. Parker was working on a speech he expected to deliver the following day before the Chamber of Commerce.

"Well, I'm glad you finally decided to come home," he remarked severely. "Since my little daughter became Tillie the Toiler, she seems to have developed independent hours."

"Wait until you hear where I've been," Penny said, sinking into an easy chair beside his desk. "Dad, you won't blame me for staying out late when I tell you what I saw and heard."

Eagerly she related all that had occurred, and was pleased to note that the story interested her father.

"Tell me more about Professor Bettenridge," he urged. "Describe him."

"He looks very scholarly, but his language doesn't fit the part," Penny recalled. "He's tall and thin and his nose is very pointed. Middle aged, which might mean forty-five or maybe fifty. That's about all I noticed except that he has a quick way of darting his eyes about. And he wears glasses."

"From your description, he sounds like the same person I heard about this afternoon," Mr. Parker commented.

"Someone told you of his experiments at the lake?"

"Quite the contrary. An Army officer, Major Alfred Bryan called at my office this afternoon, seeking information about a man who may be Professor Bettenridge."

"Was he interested in buying the machine for the Army, Dad?"

Mr. Parker dipped his pen in ink, wrote a few lines, and then looked up again. "No, Major Bryan was sent here to trace a man who has several charges against him. At one time he impersonated an officer and in recent months has been swindling persons by various schemes. He pretends to sell Army or Navy surplus war goods."

"That doesn't sound like Professor Bettenridge, Dad."

"Perhaps not, but from your description it could be the same man. This secret ray machine business sounds phoney to me. Most crooks try more than one game--the mine exploding trick may be his latest scheme to fleece gullible victims."

"Do you think we should report the professor to the police, Dad?"

"It might be a better idea to send Major Bryan to see him," Mr. Parker returned thoughtfully. "If the professor should prove to be the man he's after, then the Army would take over."

"Where is Major Bryan now, Dad?"

"He didn't mention the name of his hotel, because at the time he called at my office, I had no thought I could assist him in any way. However, he expected to stay in Riverview several days. It shouldn't be so hard to trace him. I'll get busy tomorrow."

Tired from her adventures of the night, Penny soon went to bed. The next day Mr. DeWitt gave her several interesting assignments, and when one of the stories appeared in the final edition of the _Star_, it bore a neat little "By Penny Parker," under the headline.

"Getting on in the world, I see," Elda Hunt observed sarcastically.

Not even the unkind remark could dull Penny's pleasure. She had earned her way on the newspaper by hard, routine work. The by-line meant that she had turned in an excellent well-written story. Elda, whose writing lacked crispness and originality, only once had seen her own name appear in the _Star_. Penny felt a trifle sorry for her.

"There's no fairness around here," Elda complained in a whine. "I've worked over a year. What do I have to show for it? Not even a raise."

Penny did not try to tell the girl it was her own fault, that her attitude toward her work was entirely wrong. Elda must learn for herself.

Not until Wednesday did Penny have a chance to ask her father if he had traced Major Bryan.

"To tell you the truth, the matter slipped my mind," he confessed ruefully. "I've had one conference after another all day long. Tomorrow I'll certainly try to find him."

Penny reminded him of his promise on the following day. Mr. Parker, after telephoning several places, found the major registered at the St. Regis Hotel, not far from the Parker home. However, the army officer had left for the day, and was not expected to return before nightfall.

"Oh, dear," fretted Penny, "that may be too late. If Professor Bettenridge is successful in his demonstration tonight, he may rake in Mr. Johnson's money and skip town before the major even sees him."

"It's unlikely the professor will leave without cashing the check, Penny. And banks will not be open until nine o'clock tomorrow."