Signal in the Dark Part 31

"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 sh.o.r.e. 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.