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.”