Part 7

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."

"I'd feel safer to have police take over," Penny sighed. "If only we could prove charges against Bettenridge!"

"He hasn't swindled anyone yet," her father reminded her. "Learn what you can tonight, and if the sale goes through, we'll then turn him over to the police."

"It may be too late then."

"I think not," smiled her father. "You always were a little impatient, Penny."

Eagerly Penny awaited the arrival of evening and another adventure at Blue Hole Lake. She and Salt arranged to leave the office at four o'clock, hoping to reach the farmhouse early enough to observe what preparations Webb made for exploding Mr. Johnson's mine.

But at three, Salt was sent on an important assignment.

"I'll get back as soon as I can," he promised Penny, pausing beside her desk. "I may be a little late, but we'll still make it."

"I'll be right here waiting," Penny grinned.

At ten minutes past four Salt returned. Thinking he might have pictures to develop before he would be free to leave, Penny did not rush him by going back to the photography room right away. When she had typed her last story of the day and brought it to the editor's desk for inspection, she gathered up her purse and hat.

"Leaving early, aren't you?" Elda inquired in a loud voice so that everyone would notice.

"That's right," Penny replied, without explaining her special mission.

Not wishing to leave the city without ample funds, she first went downstairs to cash a pay check at the company treasurer's window. He gave her the crisp five dollar bills, joking with her about skipping town with so much money.

Penny tucked the bills into her purse and was turning to go back upstairs again, when through the window she saw a man coming down the alley from the rear of the _Star_ building. Recognizing him as Mr. McClusky, the deep sea diver she had assisted, she darted to the window and rapped to attract his attention.

Not hearing her, he walked hurriedly on, and was lost in the crowd of the street.

"Wonder what he was doing here?" she thought as she slowly climbed the stairs. "Perhaps he came to see me. But in that case, he probably would have come up the front way."

Dismissing the matter from her mind, she sought Salt in the photography room. The outside gallery was empty, though the photographer's hat and coat hung on a hook by the window.

"Salt!" she called, thinking he must be in the darkroom.

No one answered. Nevertheless, a strange feeling Penny could not have explained, took possession of her. She sensed a presence somewhere near as if she were being watched.

Nervously Penny stepped to the door of the darkroom. She tapped lightly on it, but there was no answer.

Suddenly fearful, she jerked open the door and groped for a light. As the tiny room blazed with illumination, she uttered a startled gasp.

Almost at her feet, cheek against the floor, lay Salt Sommers.

CHAPTER 18 _A SECOND TEST_

As Penny knelt beside Salt, he stirred slightly and raised a hand to his head. She saw then that there was a tiny break in the skin which also was slightly discolored. Either the photographer had fallen or he had been slugged.

Before she could go for help, he sat up, staring at her in a bewildered manner. Penny assisted him to a chair, and dampening a handkerchief with water from the tap above the developer trays, applied it to his forehead.

"What happened?" she inquired anxiously when Salt seemed able to speak.

"Slugged," he answered in disgust.

"By whom?"

"Don't know. The fellow must have been in the darkroom when I came here to develop my films. Fact is, I thought I heard someone moving around. I stepped to the door to see, and bing! That's the last I knew."

"Has anything been taken, I wonder?" Switching on another light, Penny glanced over the room. The drawer of a filing cabinet where old films, and plates were kept, remained open.

"Someone may have been looking in there!" she commented. "Salt, whoever he is, he must be searching for a film he is afraid we'll publish in the paper."

"Maybe so," Salt agreed, holding a hand to his throbbing forehead. "But I don't know of any picture we have that would damage anyone."

Penny stepped to the doorway of the darkroom. In the larger room, the skylight remained closed. It was impossible to tell if anyone had entered the building in that way.

Some distance down the hall was a seldom-used stairway which led to the roof. Finding a door opening into it, Penny climbed the steps to look about. The rooftop was deserted, but in the building directly across from the _Star_, a corridor window remained open.

"How easy it would be for a man to step out onto the roof from there," she thought. "If the skylight or the stairway door were unlocked, he easily could enter the _Star_ photography room without being seen."

Across the way, in the adjoining building, a man stood at an office window, watching Penny curiously. Sun glared on the panes so his face was distorted. But from the location of the window, she felt certain it was Mr. Cordell.

After a moment, Penny turned and went back down the stairs. The exit at its base was barred by a door with a rusty key in the lock.

Passing through, Penny locked it, and slipped the key into her purse.

"That should stop our prowler for a few days," she thought.

In the photography room again, she checked the skylight, and finding it locked, was convinced that this time the mysterious visitor had entered the building by means of the stairs. She knew the door was usually kept locked, but undoubtedly the janitor had been careless.

By this time Salt was feeling much better. While Penny waited, he explained to the editor why the photos would not be ready until morning, then declared he was ready to start for Blue Hole Lake.

"Do you really feel like going?" Penny asked dubiously.

"Sure thing," the photographer insisted. "It takes more than a little tap on the head to put me out of running."

Salt walked a trifle unsteadily as they went down the back stairs together, but once they were in the press car, he seemed his usual jovial self.

"Now tell me about that plan of yours for tonight," Penny urged as they jounced along the country road.

"It's not much of a plan," the photographer confessed ruefully. "First, we've got to learn exactly what Webb does to those mines to make them explode. Then somehow we'll have to undo the work to cause the demonstration to turn out a flop."

"It sounds like a big order," Penny sighed. "We'll need plenty of luck to carry it out. Especially as we're arriving rather late."

Having no intention of announcing their presence, the pair drew up about a quarter of a mile from the lake, parking in a side road.

Shadows were casting long arms over the ground as they started hurriedly across the fields toward the beach. They had covered two thirds of the distance when Penny suddenly caught Salt's arm, pointing toward the lake.

"Look!" she exclaimed. "There they are now!"

Out on the lake a barge-type boat was being steered toward the beach near the shack where Professor Bettenridge stored the mines. The watching couple recognized three persons aboard the craft, the professor, Mr. Johnson and Webb. The barge also bore a large mine, similar in type to those Penny had seen inside the shack.

"That must be the mine Mr. Johnson is supplying for the test tonight," she whispered.

Hand in hand, Penny and Salt crept closer to the shore. The boat grated on the sand and Webb, with the professor helping him, carried the heavy mine toward the building.

"If the mine is to be exploded tonight, wouldn't it be easier to leave it on the barge ready to drop into the lake?" Penny commented. "Webb and the professor must have a special reason for hauling it ashore."

"I think you have something there," Salt observed. "Obviously, they're going to doctor it in some way. We'll see what happens."

Webb unlocked the door of the shack and the two men carried the mine inside. Creeping still closer to the building, Salt and Penny heard Mr. Johnson say:

"Just a minute. I see you have other mines stored here. How am I to be sure that the one exploded will be the mine I have provided?"

"You may mark it if you wish," the professor replied. "In fact, we prefer that you do, so there can be no possible doubt in your mind. Take this pocket knife and scratch your initials on the covering of the mine. Then tonight, before it is dumped in the lake, you may check again to see there has been no substitution."

"You understand, I don't distrust you," Mr. Johnson said, ill at ease. "But so much money is at stake--"

"I understand your attitude perfectly," the professor replied. "Certainly you are entitled to take every precaution."

A silence ensued, and Penny and Salt assumed that Mr. Johnson was scratching his initials on the mine.

"Now suppose we have dinner at the village inn," the professor presently suggested. "Then we will have the demonstration."

"Must we wait so long before setting off the mine?" Mr. Johnson inquired.

"Yes, village authorities gave permission for the test to be held at nine o'clock," the professor explained. "My own preference would be to get it over immediately, but I dare not disobey their orders."

Mr. Johnson made no reply, and a few minutes later, the three men walked away. No sooner had they disappeared up the lake than Penny and Salt came out of hiding from among the trees.

"You have to hand it to Professor Bettenridge," commented the photographer with grudging praise. "He's a smooth talker. I'll bet a frosted cookie the test could be held at one time as well as another so far as the village authorities are concerned. He has a special reason for wanting it at nine o'clock."