Chapter IV: Part 4

"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."

"Probably to give Webb time enough to work on the mine or exchange them," Penny said, and then frowned thoughtfully. "But what if the machine actually should work? After all, the professor agreed to explode Mr. Johnson's mine, and apparently he's marked it with his initials. It won't be easy to substitute another one now."

"All the same, if I'm any good at guessing, it will be done. Now what shall we do until nine o'clock? Grab ourselves something to eat?"

Penny was about to suggest that they drive to a village cafe, when she noticed Webb returning alone from up the beach. Barely did the pair have time to duck out of sight behind a boulder before he approached.

Walking directly to the shack, he unlocked the door, and entered.

"Now this must be where the hocus-pocus begins!" Salt whispered. "We've got to find out what he does to that mine."

"Louise and I climbed up in that tree the other day and looked through the glass in the top."

"Then that's the trick for us! Come on!"

Making no sound, the pair climbed the tree close beside the shack. Noiselessly, they inched their way toward the skylight, and lying flat, peered down into the dark interior.

Webb had lighted a lantern which he hung on a wall nail. Unaware that he was being watched, he squatted in front of the mine which bore Mr. Johnson's initials, studying it thoughtfully.

Muttering to himself, he next took a powerful ratchet drill, and for a long time worked with it on the mine, boring a tiny but deep hole.

"I'm getting stiff in this position," Penny whispered. "What is he doing, Salt?"

"Don't know," the photographer admitted, puzzled. "Apparently, he's doctoring Mr. Johnson's mine so it will explode tonight, but I'm not smart enough to figure how the trick will be accomplished."

By now it was so dark that the pair in the tree no longer feared they would be seen. Keeping perfectly still, they watched the work in the room below.

"It's clear why Professor Bettenridge set nine o'clock for the demonstration," Salt whispered. "Webb needed all this time to get the mine ready."

"And that's why they brought it here instead of dumping it into the lake," Penny added. "But how can they make the mine explode at exactly the right moment?"

After Webb had worked for a while longer, he arose and stretched his cramped muscles. Going to a cupboard, he removed a white powder from a glass tube, and carefully inserted it in the hole he had just made in the mine. As a final act, he sealed the tiny hole with another material, and polished the surface so that the place did not show.

"Slick work!" Salt commented. "By the time he's through, no one ever could tell the mine has been touched! Certainly not that thick-skulled Johnson."

Apparently satisfied with his work, Webb put away his tools, made a final inspection of the mine, and then left the shack. After carefully locking the door, he disappeared into the night.

"Now what's our move?" Penny asked as she and Salt finally slid down from their uncomfortable perch. "Shall we tell Mr. Johnson what we just saw?"

"We could, but he might not believe us. Penny, I have a better idea! If we can get inside the shack--"

"But it's locked!"

"The skylight may be open." Salt climbed up on the roof to investigate, but to his disappointment, the roof window was tightly fastened from inside.

"We could smash the glass," Penny suggested dubiously.

Salt shook his head. "That would give the whole thing away. No, I think we can get inside another way, but we'll have to work fast! Now that Webb has the mine ready for the demonstration, the professor and Mr. Johnson may show up here at any minute."

CHAPTER
19
_THE LANTERN SIGNAL_

Salt explained that he intended to pick the lock of the shack door.

"When I worked the police beat, a detective taught me this trick," he explained. "You keep watch while I work."

Now that Webb had disappeared no one was to be seen near the beach. To Penny's relief, not a person appeared, and Salt, working swiftly, soon had the door open.

To make certain they would not be taken unawares, Salt relocked the door on the inside. Groping about, he found the lantern Webb had left behind, and lighted it.

Three mines lay on the floor. "Which is the right one?" Penny asked. "They all look alike!"

"Mr. Johnson's initials must be on the one Webb tampered with."

Salt turned over one of the mines, inspecting it.

"That thing might go off any minute," Penny said, edging away. "Do be careful, Salt."

Salt chuckled. "If it should go off, we'd never know what hit us," he said. "This is the one Webb tampered with all right. Penny, how are you at forging?"

"Forging?" she repeated, not understanding what he meant.

"Can you duplicate Mr. Johnson's initials on another mine?"

"Oh, I don't think so. Not so it would look the same."

"Sure, you can," Salt said, thrusting his pocket knife into her hand. "It will be dark and no one will look too carefully."

"But why do you want me to do it? You mean to substitute Mr. Johnson's mine for one of the others?"

"That's the ticket," chuckled the photographer. "Maybe my guess is wrong, but I have a sneaking suspicion if we use one of the professor's own mines, it will fail to explode."

"The mine has to be doctored with that powder we saw Webb use!"

"That's my theory, Penny."

"But maybe the other mines have already been treated."

"That's a possibility," Salt admitted thoughtfully. "No way of telling that, because the hole would be covered so skillfully. We'll have to take a chance on it."

While Salt held the lantern, Penny scratched Mr. Johnson's initials on the metal covering of the mine. Skilled in art, she was able to copy them fairly well.

"They don't look exactly the same," Salt said, comparing the two, "but they're good enough to get by unless Mr. Johnson becomes very critical."

Quickly they moved the two mines, placing Mr. Johnson's well to the back of the room, and leaving the substitute exactly where the other had been.

"Well, that job is done," Salt chuckled. "Unless I miss my guess--"

He broke off, startled to hear a murmur of voices from a short distance down the beach. Quick as a flash he blew out the lantern and hung it in its accustomed place on the wall nail.

"Salt! Those men are coming!" Penny whispered fearfully. "We're trapped here!"

It was too late to slip out the door, for already the men were very close, and unmistakably, one of the voices was that of Professor Bettenridge.

The only available hiding place was a storage closet. Barely in time, Salt and Penny squeezed into it, closing the door and flattening themselves against the wall.

The door of the shack swung open to admit the professor, Webb, and Mr. Johnson.

"Dark as pitch in here," Webb muttered. "Wait and I'll light the lantern."

In a moment the yellow glow illuminated the dingy little room.

"Which is my mine?" Mr. Johnson asked. "They all look alike."

"And for all practical purposes they are exactly alike," said the professor smoothly. "So far as my machine is concerned, it makes not a particle of difference. Webb, which is the mine that Mr. Johnson supplied?"

"Here it is," the assistant said, tapping the one Salt and Penny had substituted. "See your initials, Mr. Johnson?"

"Yes, yes," agreed the man.

Inside the closet, Penny and Salt breathed easier.

"Let's get on with the demonstration," the professor urged with sudden impatience. "Load the mine onto the boat, Webb. Go out to the center of the lake. Then when you have dropped it, give the usual signal."

"When everything is okay, I'll wave my lantern three times," Webb agreed.

The mine was trundled out and the shack became dark. However, Salt and Penny did not dare come out of hiding until they heard Webb start the motor of the boat.

"The coast is clear," the photographer then reported, peering out a crack of the outer door. "Webb has gone, and the professor and Mr. Johnson are walking up to the cabin."

From the beach, Penny and Salt watched the boat moving slowly across the water. Presently the craft stopped, and the mine was heaved overboard. The pair waited, but there was no signal from Webb. Nor did his boat move away from the locality where the mine had been dropped.

"Why doesn't he wave the lantern?" Penny fretted.

"He's waiting deliberately, and for a purpose," Salt declared. "Why not amble up the hill and watch the professor perform?"

"Not a bad idea," agreed Penny.

Walking rapidly, they arrived at the cabin quite breathless. As they tapped lightly on the door, Professor Bettenridge appeared visibly startled. He stiffened to alert, guarded attention, but relaxed slightly as his wife admitted the pair.

"Oh, it's you two again," he said none too pleasantly. "You are just in time to witness my final demonstration. We are waiting now for my assistant's signal."

"It seems to take a long while," Mr. Johnson commented, glancing at his watch.

"Webb may have had trouble getting the mine overboard," the professor soothed. "Besides, he has to move out of the danger zone."

Penny and Salt looked at each other but said nothing. They were certain that Webb had been in no haste to return to shore.

"What are you two smirking about?" the professor demanded irritably. "I suppose you think my machine won't work?"

"I'll be surprised if it does," Salt agreed, unruffled.

Mrs. Bettenridge, who stood at the window, suddenly cried: "There is the signal!"

Professor Bettenridge snapped on a switch and the ray machine began to hum. He turned on another motor and lights began to glow. Then he struck the crystal ball, producing a musical vibration.

Assuming a confident pose, he waited.

Nothing happened.

As the seconds ticked by and still there was no explosion, the professor began to wilt. He gazed desperately at his wife who looked as dismayed as he.

"My dear, something seems to be wrong. Are you sure you saw the signal? Perhaps Webb has not yet dropped the mine."

"I saw the signal. The lantern was waved three times."

The professor made several adjustments on his machine, and again struck the musical note. But there was no explosion. Enjoying his discomfiture, Salt and Penny grinned from ear to ear.

"You did something to the machine!" the professor accused them furiously. "You came here and tampered!"

"We've not been near this place tonight until a moment ago," Penny retorted. "The truth is, you weren't able to explode Mr. Johnson's mine!"

"That's not so!" The professor's face now was red with anger. "Something has gone wrong, but that doesn't prove my machine is a failure. We'll have another test."

"I'm not sure that I shall be interested," Mr. Johnson said quietly. "I've been thinking the matter over and there are so many hazards--"

"I'll make you an especially good offer," the professor declared, flipping the canvas cover over his machine. "Furthermore, we will have the test tonight. I guarantee to explode the mine before you leave here."

"But the mine I supplied is at the bottom of the lake and it failed to go off," Mr. Johnson said.

"First, we will talk to Webb and learn exactly what happened," the professor said, taking him by the arm. "I know there is a logical explanation for the failure."

Glaring at Penny and Salt, he shooed everyone out of the cabin, locking the door.

"My dear," he said to his wife, giving her a significant look, "take Mr. Johnson to the house while I find Webb. I'll be with you in just a minute."

The professor went hurriedly down the beach while Mrs. Bettenridge and Mr. Johnson walked slowly toward the rooming house. Penny and Salt remained beside the cabin until everyone was beyond hearing.

"Well, our trick worked," Salt chuckled, "but if we aren't careful, the professor will pull off a successful test yet and ruin all our plans."

"He and Webb are certain to examine the mines and discover the one with Mr. Johnson's initials still in the shack. Then they may convince Mr. Johnson there was a mix-up, and go ahead with another test which will be successful."

"We've got to do something," Salt muttered. "But what?"

"I know!" Penny exclaimed. "I'll telephone Dad and have him come here right away with Major Bryan!"

"Good!" approved Salt. "I'll stay here and hold the fort while you telephone. Tell your father to step on the gas, because we've got to move fast to queer Professor Bettenridge's game."

CHAPTER
20
_A CROOK EXPOSED_

Eager to carry out Salt Sommers' bidding, Penny ran up the hill in search of a telephone. She considered using the one at the house where Professor and Mrs. Bettenridge roomed, but decided against it, fearing that the conversation might be overheard or reported to them by the farm woman.

Hastening on, she saw a light farther down the road, and recalled having noticed a house there. Five minutes later, completely winded, she pounded on the door. A man in shirtsleeves, the evening newspaper in his hand, answered her knock.

"Please, may I use your telephone?" Penny gasped.

"Why, sure," he agreed, stepping aside for her to enter. "Anything wrong?"

Penny knew better than to mention what was happening at the lake. "I want to telephone my father in Riverview," she explained.

"The phone is in the other room," the man said, switching on a light.

Placing the call, Penny waited impatiently for it to be put through. She was uncertain whether her father would be at home. If she failed to reach him, then the only other thing was to notify the sheriff.

"Here is your party. Go ahead, please," came the long distance operator's voice. The next moment Penny heard her father's clear tones at the other end of the line.

"Dad, I'm at Blue Hole Lake with Salt," she explained hurriedly. "Can you drive here right away?"

"I suppose so," he answered, knowing from her voice that something serious was wrong. "What's up?"

"We've learned plenty about Professor Bettenridge, Dad. Unless something is done quickly, he may sell his fake machine to Mr. Johnson."

"But what can _I_ do about it?" the publisher asked.

"Can you get hold of the Major and bring him with you?" Penny pleaded. "Professor Bettenridge may be the man he's after!"

"Maybe I can reach him!" Mr. Parker agreed. "If I have luck I'll be out there within twenty or thirty minutes. I'll come as fast as I can."

Before hanging up the receiver, Penny gave her father detailed instructions for reaching the lake and told him where to park. Leaving a dollar bill to pay for the call, she then hastened back to find Salt.

The photographer was nowhere near the cabin and she was afraid to call his name lest she be overheard by the Bettenridges.

As she stood in the shadow of the building, she heard voices from the beach. Someone with a lighted lantern was coming up the trail, and soon she distinguished two figures--Professor Bettenridge and Webb.

"That's the story you'll have to tell Johnson," she heard the professor say. "Tell him that somehow you got the two mines mixed up as you were loading them onto the boat and dumped one that was never meant to explode."

"But he saw us load the mine."

"It was dark and he may not be sure. Anyway, the mine with Johnson's initials is still in the shack. We'll show it to him."

"What bothers me is how did the mistake happen?" Webb muttered. "I know the mine I loaded on the boat had Johnson's initials. It should have gone off."

"Someone is onto our game, and tampered with the mines. It may have been a trick of that newspaper pair."

"In that case, we're in a dangerous spot. We ought to clear out while the clearing is good. If the authorities get onto what we're doing--"

"They won't--at least not tonight," the professor said confidently. "The sheriff is as dumb as they come, and is convinced I am a genius second only to Thomas Edison. We'll have to pull off a successful test tonight with Johnson's mine, collect what we can, and clear out."

"Okay," Webb agreed, "but this is my last job. The game is too dangerous. I served one stretch in the pen and I don't look forward to another."

"If we can explode Johnson's mine tonight, we'll collect the money and be away from here as soon as we cash the check. Can you pull off the job without any blunder?"

"Sure I can unless someone tampers with the mine! This time I'll make sure they don't!"

"Okay," the professor agreed. "Now I want you to talk to Johnson. Put up a good story, and get him to look at the mine that has his initials on it. If he refuses, we're licked, but it's worth a final try."

"I'd like to find the guy who broke into the shack!" Webb muttered.

"We may have time for that later. Just now our most important job is to convince Johnson we have something to sell."

The two men now were very close. Penny flattened herself against the building wall, fearful of being seen. The light from their lantern illuminated her for an instant, but the men were so absorbed in their discussion, they failed to see her. Going on up the hillside path, they vanished into the farmhouse.

What had become of Salt, Penny did not know. Thinking he might have gone down to the lake, she walked rapidly in that direction. As she approached the shack where the mines were stored, she heard a low whistle.

"Is that you, Salt?" she called softly.

He came from behind a clump of bushes to join her. Quickly they compared notes. Salt had overheard no conversation, but he had watched Professor Bettenridge and Webb as they reexamined the mines in the shack.

"They're onto our game, and it won't work twice," he said. "We've got to delay the test, but how?"

"Maybe we could cut the boat loose!"

"A capital idea!" Salt approved, chuckling. "Penny, you really have a brain!"

As they scurried over the stones to the water's edge, Penny suddenly stopped short.

"Listen!" she commanded.

"I didn't hear anything," Salt said.

"An automobile stopped by the roadside. I'm sure of it. Maybe it's my father!"

"He couldn't have reached here so soon."

"You don't know Dad," Penny chuckled. "He drives like the wind. It certainly sounded like the engine of our car."

"Let's have a look before we cut the boat loose," Salt said, slipping a knife back into his pocket.

"I'll go," Penny offered. "You wait here."

Before Salt could stop her, she darted away into the darkness. Crawling under a barbed wire fence, she took a short cut to the road. Even before she saw the car, she heard a voice which she recognized as her father's.

"Dad!" she called softly.

He was with another man whom Penny hoped was Major Bryan. As the two came toward the fence, she saw that it was indeed the Army officer.

"Dad, how did you get here so quickly?" she greeted him. "Salt and I didn't expect you for at least another twenty minutes."

"I was lucky enough to get hold of Major Bryan right away," Mr. Parker answered, climbing over the fence. "Now I hope you haven't brought us on a wild chase, Penny. What's up?"

"Come with me and I'll show you," she offered. "That's easier than explaining everything."

Major Bryan, a well-built man of early middle age, asked Penny several questions about Professor Bettenridge as the three walked hurriedly toward the lake.

"From your description, he seems to be the man I'm after," he declared grimly. "If he's the same person, his real name is Claude Arkwright and he's wanted for impersonating an officer and on various other charges. He pulled a big job in New York three months ago, then vanished."

Salt was waiting at the lake. "What's our move?" he asked, after relating everything that had occurred that night. "Shall we cut the boat loose?"

"First, let me examine those mines," the major requested. "Can we get into the shack?"

"I can pick the lock, but it takes time," Salt offered.

"We'll break it," the major decided. "Those men may return here at any minute, so there's no time to lose."

The door was forced open and Penny was placed on guard to watch the hillside for Webb or anyone in the professor's party.

There was no light in the shack, but both Mr. Parker and the major had brought flashlights. Salt pointed out the mine which had been doctored by Webb. Carefully, the Army officer examined it.

"I can't tell much by looking at it for the work has been cleverly concealed," he admitted. "But from what you've told me, I am quite certain how the mine is made to explode."

"How is it done?" Salt demanded.

"After the hole is made, a chemical--probably sodium--is inserted. Then another substance which melts slowly in water is used to seal up the opening."

"Then that explains why Webb delayed so long in giving the signal after the mine had been dropped into the water!" Penny exclaimed from the doorway. "He was waiting for the substance to melt!"

"Exactly," agreed the major. "If my theory is correct, only the action of water is required to explode this mine. The professor's machine, of course, has nothing whatsoever to do with it."

"Why don't we explode the mine now?" Penny suddenly proposed. "That would put an end to the professor's little scheme."

"It might also prevent us from arresting him," the major said. He debated a moment. Then he exclaimed: "It's worth trying! We'll load the mine on the boat and dump 'er in the lake!"

The men would not permit Penny to help with the dangerous work. Carefully they transported the mine to the boat. Salt was about to start the motor, but the major stopped him.

"No, we don't want the sound of the engine to give us away," he said. "We'll row out into the lake."

Penny was eager to accompany the men, but they would not hear of it. To her disappointment, she was compelled to remain on the beach.

Sitting down on the sand, she nervously watched until the boat faded into the black of the night. Presently, she heard a splash which told her that the mine had been lowered overboard. Anxiously, she waited for the boat to return.

"Why don't they come?" she thought, straining to hear the sound of oars. "If the explosion should go off while they're still out there--"

Then she heard the boat coming and breathed in relief. Soon the craft grated on sand, and the three men leaped out.

"Perhaps my theory is wrong," the major commented, as they all huddled together, waiting. "The mine should have gone off by this time."

Several minutes elapsed and still nothing happened. And then, as the group became convinced their plan had failed, there came a terrific explosion which sent flame and water high above the lake's surface.

CHAPTER
21
_IN SEARCH OF WEBB_

"Beautiful! Beautiful!" chuckled the major as the flames began to die away. "That proves our theory. No machine is required to set off the mines--only the action of water."

"Professor Bettenridge must have heard the explosion!" Penny exclaimed, fairly beside herself with excitement. "What will happen now?"

"If human nature runs true to form, he will soon come here to investigate," the major predicted.

The four stepped back into the dense growth of trees to wait. Within five minutes they observed two shadowy figures scurrying down the path toward the shack where the mines were stored. As they came closer, Penny recognized the professor and his wife.

"And someone is following them," she discerned. "It looks like Mr. Johnson."

Professor Bettenridge and his wife now were near the trees. Their voices, though low, carried to those in hiding.

"That stupid lout, Webb!" the professor muttered. "He has ruined everything now by setting off the mine too soon."

"But how could it have been Webb?" his wife protested. "He was at the farmhouse only five minutes ago. He wouldn't have had time."

"Then it was someone else--" Professor Bettenridge paused, and cast a quick alert glance about the lake shore. He noted that the boat was tied, but that the door of the shack was wide open.

"We've been exposed!" he muttered. "Our game is up, and we've got to get away from here before the authorities arrest us."

"But what about Johnson?" his wife demanded, glancing over her shoulder at the man who was following them down the hillside path.

"We can do nothing now. He had begun to catch on even before tonight, and this explosion finishes everything. Don't even stop to pack your clothes. We'll get our car and clear out."

"Webb?"

"He'll have to look out for himself. We're traveling alone and traveling fast."

Those in hiding suddenly stepped forth from the trees, blocking the path. Major Bryan moved directly in front of the professor, flashing a light into his face.

"Good evening, Claude Arkwright," he said distinctly.

The professor was startled, but recovered poise quickly. "You are mistaken," he said in a cold voice. "My name is Bettenridge."

"No doubt that is what you call yourself now. You are wanted by the Federal government for impersonating an officer."

"Ridiculous!"

"May I see your draft card?" the major requested curtly.

"Sorry, I haven't it with me. It is in my room."

"Then we will go there."

Nettled, Professor Bettenridge could think of no further excuse. Glancing significantly at his wife, he said: "My dear, will you go to the house and get the card for our inquisitors?"

"We will all go," corrected the major. "Your wife may be wanted as your accomplice in this latest secret ray machine fleece. We prefer that she does not escape."

"You are very trusting," sneered the professor.

By this time, Mr. Johnson had reached the hillside. Puffing from having hurried so fast, he gazed in bewilderment at the little group.

"What does this mean?" he inquired. "What caused the mine to explode?"

"It was set off by being dropped in the lake," explained the major.

"You mean the explosion was not touched off by Professor Bettenridge's invention?"

"The machine had nothing whatsoever to do with it," Penny explained. "Professor Bettenridge and his accomplice, Webb Nelson, have been doctoring the mines with a powder and an outer shield which dissolves in water. They hoped to sell the worthless machine to you before you discovered the truth."

The information stunned Mr. Johnson, but recovering, he turned furiously upon Professor Bettenridge.

"You cheap trickster!" he shouted. "I'll have you arrested for this!"

"Have you given the man any money?" Mr. Parker inquired.

"A thousand dollars for an option on the machine. The rest was to have been paid tonight."

"You're lucky to get off so easily," Mr. Parker said. "It's possible too, that we can get part of your deposit back."

"You can't hold me on any trumped-up charge," Professor Bettenridge said angrily. "You have no warrant."

He started away, but was brought up short as he felt the major's revolver pressing against his ribs.

"This will hold you, I think," said the Army man coolly. "Now lead the way up the hill to the other cabin. I want to see your remarkable invention."

With his wife clinging to his arm, the professor marched stiffly ahead of the group. He unlocked the cabin door and all went inside.

Jerking off the canvas which covered the secret ray machine, Major Bryan inspected it briefly.

"A worthless contraption!" he said contemptuously. "Utterly useless!"

"Where did you meet Webb Nelson?" Penny asked the professor. "And where is he now?"

"You'll have to find him for yourself," sneered the professor. "If he has the sense I think, he's probably miles away from here by now."

Determined that the man should not escape, Penny, Salt and Mr. Parker started for the farmhouse, leaving the major and Mr. Johnson to question the professor. As they rapped on the screen door, Mrs. Leonard came to let them in.

"What is going on here tonight, may I ask?" she demanded irritably. "People banging in and out of the house at all hours! Explosions! I declare, I wish I never had rented a room to that crazy professor and his wife!"

"Is Webb Nelson here?" Mr. Parker asked.

"The professor's helper? Why, no, right after the explosion he came, gathered a bag of things from the professor's room, and went off down the road."

"In a car?"

"He was afoot when he left here. Is anything wrong?"

"Considerable. Professor Bettenridge has just been exposed as an impostor. Webb must have realized the jig was up when he heard the mine go off."

"The professor an impostor!" Mrs. Leonard exclaimed. "Well, of all things!"

"Which way did Webb go?" Mr. Parker asked.

"Down the road toward town when I last saw him."

"Maybe we can catch him!" Mr. Parker cried.

"If he didn't get a lift," Salt added.

All piled into the Parker car which had been left a short distance down the road. But in the drive to Newhall, the man was not sighted. Nor did inquiry in the town reveal anyone who had seen him.

"Undoubtedly he expected to be followed, and cut across the fields or took a side road," Mr. Parker declared. "We'll have to depend upon the authorities to pick him up now."

Stopping at the sheriff's office, warrants for the man's arrest were sworn out, and the party then returned to Mrs. Leonard's. Professor Bettenridge and his wife had been brought to the farmhouse by Major Bryan who proposed to hold them there pending the arrival of federal authorities from Riverview.

"There's one thing I want to know," Penny whispered to her father. "How did Professor Bettenridge meet Webb? Perhaps he can explain the man's connection with the _Snark_."

The question was put to the professor who replied briefly that he knew nothing whatsoever about Webb Nelson.

"I met him only two weeks ago," he said. "He claimed to be an expert at handling explosives, so I hired him."

No one believed the professor was telling the truth. However, it was useless to question him further. Determined not to implicate himself, his wife, or his helper, he spoke as seldom as possible.

"The man has a room here," Mr. Parker suggested. "Suppose we see what we can find."

Mrs. Leonard led the way upstairs. The professor's room was locked, but she opened it with a master key.

Two suitcases had been packed as if for a hasty departure and everything was in disorder. All garments had been removed from the closets. The scrap basket was filled with torn letters which Mr. Parker promptly gathered together and placed in an envelope for future piecing together.

In one of the suitcases he found several newspaper clippings. One bore a picture of the professor, but the name beneath it was Claude Arkwright, and the story related that he was wanted in connection with a $10,000 hoax.

"Bettenridge is our man all right," the publisher declared. "We made no mistake in holding him for the sheriff."

Penny had been searching the larger of the two suitcases which seemed to contain only clothing. But as she reached the lower layer, she suddenly gave a jubilant cry.

"Salt! Dad!" she exclaimed. "It's here! See what I've found!"

CHAPTER
22
_SALT'S MISSING CAMERA_

From the suitcase, Penny lifted Salt's camera. With a cry of pleasure, he snatched it from her hand and eagerly examined it.

"Is it damaged in any way?" Penny asked.

"It doesn't seem to be. So the professor had it all the time just as we thought!"

"And here are the plates I tossed into the car the night of the explosion!" Penny added, burrowing deeper into the pile of clothing. "They're probably ruined by now."

"Maybe not," said Salt, examining them. "The professor may have thought they were unexposed plates and kept them for use later on."

"Anyway, it was crooked of him to try to keep the camera," Penny declared. "Though I suppose such a small theft doesn't amount to much in comparison to the trick he nearly played on Mr. Johnson."

"It matters to me," the photographer chuckled. "Am I glad to get this camera back! The plates won't do us any good now they are outdated, but I'll take them along anyhow. I'm curious to see if they would have shown anything of significance."

"By all means develop them," urged Mr. Parker. "Anything else in the suitcase?"

In a pocket of the case Penny found several letters from Mr. Johnson which she gave to her father. Knowing they would be valuable in establishing a case of attempted fraud against the professor, he kept them.

"I wish Webb Nelson hadn't managed to escape," Penny remarked as the trio went downstairs again. "He must have started for Newhall, perhaps to catch a train."

"Any due at this time?" her father asked thoughtfully.

"I wouldn't know."

"Tell you what," Mr. Parker proposed. "We can do nothing more here. We may as well drive to the village again and press an inquiry for Webb."

Once more the car with Salt as driver careened over the bumpy country road to Newhall. They reached the town without sighting anyone who resembled the professor's helper.

"Drive to the station," Mr. Parker instructed Salt. "There's an outside chance Webb went there."

The depot was a drab little red building, deserted except for a sleepy-eyed station agent who told them there was no passenger train scheduled to leave Newhall before six o'clock the next morning.

"Any freight trains?" Mr. Parker inquired.

"A couple are overdue," the agent said. "No. 32 from the east, and No. 20, also westbound. No. 20's just coming into the block."

Although it seemed unlikely Webb would take a freight train out of town, Mr. Parker, Salt and Penny, decided to wait for it to come in. They went outside, standing in the shadow of the station.

"No sign of anyone around," Salt declared, looking carefully about. "We may as well go back to the lake."

"Let's wait," Penny urged.

No. 20 rumbled into the station, stirring up a whirlwind of dust and cinders. A trainman with a lantern over his arm, came into the station to get his orders from the agent. He chatted a moment, then went out again, swinging aboard one of the cars. A moment later, the train began to move.

"Shall we go?" Mr. Parker said impatiently.

Penny buttoned her coat as she stepped beyond the protection of the building, for the night air was cold and penetrated her thin clothing. Treading along behind her father and Salt to the car, she started to climb in, when her attention riveted upon a lone figure some distance from the railroad station. A man, who resembled Webb Nelson in build, had emerged from behind a tool shed, and stood close to the tracks watching the slowly moving freight.

Then he ran along beside the train and suddenly leaped into one of the empty box cars.

"Dad! Salt!" she exclaimed. "I just saw someone leap into one of those cars! I'm sure it was Webb!"

"Where?" demanded her father. "Which car?"

"The yellow one. Oh, he'll get away unless we can have him arrested at the next town!"

"He won't escape if I can stop him!" Salt muttered.

Racing across the platform, he waited for the car Penny had indicated. Although the train was moving faster now, he leaped and swung himself to a sitting position in the open doorway.

"Look out! Look out!" Penny screamed in warning.

Behind Salt, the man who had taken refuge in the car, moved stealthily toward him, obviously intending to push him off the train. But the photographer knew what to expect and was prepared.

He whirled suddenly and scrambled to his feet. His attacker caught him slightly off balance, and they went down together, rolling over and over on the straw littered floor.

Worried for Salt, Penny and Mr. Parker ran along beside the train. The publisher tried to leap aboard to help the photographer, but lacking the younger man's athletic prowess, he could not make it. Already winded, he began to fall behind.

Penny kept on and managed to grasp the doorway of the car, but she instantly realized she could not swing herself through the opening. The train now was moving rapidly and gaining speed each moment.

Inside the box car, the two men were rolling over and over, each fighting desperately to gain the advantage. Penny could not see what was happening. Forced by the speed of the train, she let go her hold. Her feet were swept from beneath her, and she stumbled and fell along the right of way.

Before she could scramble to her feet, her father had caught up with her.

"Are you hurt?" he asked anxiously.

Penny's knees were skinned but the injury was so trifling she did not speak of it. Her one concern was for Salt.

"Oh, Dad," she said, grasping his arm nervously. "What are we going to do? That brute may kill him!"

Mr. Parker shared Penny's concern, but he said calmly: "There's only one thing we can do now. We'll have the station agent send a wire to the next station. Police will meet the train and take Webb into custody."

"He may not be on the train by the time it reaches the next town! Oh, Dad, Salt may be half killed before then!"

Penny and her father stared after the departing freight. The engineer whistled for a high trestle spanning a narrow river, and the train began to rumble over it.

Suddenly Penny stiffened into alert attention. In the doorway of the open boxcar, she could see the two struggling men. Mr. Parker, too, became tense.

As they watched fearfully, one of the men was pushed from the car. He rolled over and over down a steep embankment toward the creek bed.

The other man, poised in the doorway an instant, then just before the car reached the trestle, leaped.

CHAPTER
23
_ESCAPE BY NIGHT_

Fearful for Salt, Penny and her father ran down the tracks toward the railroad trestle. Scrambling and sliding down the slippery embankment, they saw Salt lying in a heap near the edge of the creek.

Webb, his ankle injured, was trying to hobble toward a corn field just beyond the railroad right of way.

"Get him! Don't let him escape!" Salt cried, raising himself to his knees.

Although alarmed for the photographer who appeared to have been injured by his leap, Penny and her father pursued Webb. Handicapped as he was with an injured ankle, they overtook him by the barbed wire fence.

Already badly battered from the fight, and bruised as a result of his fall from the train, the man put up only a brief struggle as Mr. Parker pinned him to the ground.

"Quick!" the publisher directed Penny. "See what you can do for Salt. He may be badly injured."

The photographer, however, had struggled to his feet. He stood unsteadily, staring down at his torn clothing.

"Are you all right?" Penny asked anxiously, running to his side.

"Yes, I'm okay," he said, gingerly touching a bruised jaw. "Boy! Is that lad a scrapper? Did you see me push him out of the boxcar?"

"We certainly did, and we were frightened half to death! We thought you would be killed."

Hobbling over to the fence, Salt confronted his assailant. Webb's face was a sorry sight. His nose was crimson, both eyes were blackened and his lip was bleeding.

"You may as well come along without making any more trouble," Mr. Parker told him grimly. "Professor Bettenridge has been taken into custody, and the entire fraud has been exposed."

"I figured that out when I heard the mine go off," the man returned sullenly. "Okay, you got me, but I was only carrying out orders. I worked for Professor Bettenridge, but any deals he made were his business, not mine."

"That remains to be seen," replied Mr. Parker. "We'll let you talk to the sheriff. Move along, and no monkey business."

Having no weapon, Salt and the publisher walked on either side of the prisoner, while Penny brought up the rear.

"You don't need to hang onto me," he complained bitterly. "I ain't going to try to escape."

"We're sure you won't," returned Salt, "because we'll be watching you every step of the way."

At first, as the four tramped down the tracks toward the station, the prisoner showed no disposition to talk. But gradually his curiosity gained the better of him. He sought information about Professor Bettenridge's arrest, and then tried to build up a story that would convince his captors he had only been an employee hired on a weekly basis.

"I suppose you know nothing about the _Snark_ either," Penny observed bitterly. "After Ben Bartell and I pulled you out of the river, you repaid us by stealing his watch."

To her astonishment, the man reached in his pocket and gave her the timepiece.

"Here," he said gruffly, "give it back to him. I won't need it where I'm going."

"Why did you take the watch when it didn't belong to you?" Penny pursued the subject. "Especially after Ben risked his life to pull you out of the river."

"Oh, I don't know," the man answered impatiently. "I needed a watch, so I took it. Quit askin' so many questions."

"Why were you pushed off the _Snark_?" Penny demanded, refusing to abandon the subject.

She did not expect Webb to answer the question as he had refused to explain at the time of his rescue. To her surprise, he replied grimly:

"They tried to get rid of me. We had a disagreement over a job they wanted me to pull."

"What job was that?" Mr. Parker interposed.

"Dynamiting the Conway Steel Plant."

The words produced a powerful effect upon the publisher, Salt, and Penny. At their stunned silence, Webb added hastily:

"You understand, I didn't do it. They got sore because I refused to pull the job."

"Why, that doesn't make sense," Penny protested. "Evidently, you are mixed up on your dates, because the Conway Plant explosion took place before the night we rescued you from the water."

"Sure, I know," the man muttered, trying to cover his slip of tongue. "They were afraid I'd squawk to the police and that was why they pitched me overboard."

"Who pulled the job?" Salt asked.

"I don't know. Someone was hired to set off the explosion."