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," heexplained. "You keep watch while I work."
Now that Webb had disappeared no one was to be seen near the beach. ToPenny's relief, not a person appeared, and Salt, working swiftly, soonhad the door open.
To make certain they would not be taken unawares, Salt relocked the dooron 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 becareful, Salt."
Salt chuckled. "If it should go off, we'd never know what hit us," hesaid. "This is the one Webb tampered with all right. Penny, how are youat 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. "Itwill be dark and no one will look too carefully."
"But why do you want me to do it? You mean to substitute Mr. Johnson'smine 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 ownmines, 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 tellingthat, because the hole would be covered so skillfully. We'll have to takea chance on it."
While Salt held the lantern, Penny scratched Mr. Johnson's initials onthe metal covering of the mine. Skilled in art, she was able to copy themfairly well.
"They don't look exactly the same," Salt said, comparing the two, "butthey'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 backof 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 distancedown the beach. Quick as a flash he blew out the lantern and hung it inits accustomed place on the wall nail.
"Salt! Those men are coming!" Penny whispered fearfully. "We're trappedhere!"
It was too late to slip out the door, for already the men were veryclose, and unmistakably, one of the voices was that of ProfessorBettenridge.
The only available hiding place was a storage closet. Barely in time,Salt and Penny squeezed into it, closing the door and flatteningthemselves 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 thelantern."
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 theprofessor smoothly. "So far as my machine is concerned, it makes not aparticle of difference. Webb, which is the mine that Mr. Johnsonsupplied?"
"Here it is," the assistant said, tapping the one Salt and Penny hadsubstituted. "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 suddenimpatience. "Load the mine onto the boat, Webb. Go out to the center ofthe 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 andPenny did not dare come out of hiding until they heard Webb start themotor of the boat.
"The coast is clear," the photographer then reported, peering out a crackof the outer door. "Webb has gone, and the professor and Mr. Johnson arewalking up to the cabin."
From the beach, Penny and Salt watched the boat moving slowly across thewater. Presently the craft stopped, and the mine was heaved overboard.The pair waited, but there was no signal from Webb. Nor did his boat moveaway 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 notamble up the hill and watch the professor perform?"
"Not a bad idea," agreed Penny.
Walking rapidly, they arrived at the cabin quite breathless. As theytapped lightly on the door, Professor Bettenridge appeared visiblystartled. He stiffened to alert, guarded attention, but relaxed slightlyas his wife admitted the pair.
"Oh, it's you two again," he said none too pleasantly. "You are just intime to witness my final demonstration. We are waiting now for myassistant's signal."
"It seems to take a long while," Mr. Johnson commented, glancing at hiswatch.
"Webb may have had trouble getting the mine overboard," the professorsoothed. "Besides, he has to move out of the danger zone."
Penny and Salt looked at each other but said nothing. They were certainthat Webb had been in no haste to return to shore.
"What are you two smirking about?" the professor demanded irritably. "Isuppose 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 thesignal!"
Professor Bettenridge snapped on a switch and the ray machine began tohum. He turned on another motor and lights began to glow. Then he struckthe 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 professorbegan to wilt. He gazed desperately at his wife who looked as dismayed ashe.
"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 struckthe 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," Pennyretorted. "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. "Somethinghas gone wrong, but that doesn't prove my machine is a failure. We'llhave 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 havethe 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 gooff," Mr. Johnson said.
"First, we will talk to Webb and learn exactly what happened," theprofessor said, taking him by the arm. "I know there is a logicalexplanation for the failure."
Glaring at Penny and Salt, he shooed everyone out of the cabin, lockingthe 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 aminute."
The professor went hurriedly down the beach while Mrs. Bettenridge andMr. Johnson walked slowly toward the rooming house. Penny and Saltremained beside the cabin until everyone was beyond hearing.
"Well, our trick worked," Salt chuckled, "but if we aren't careful, theprofessor 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 withMr. 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 besuccessful."
"We've got to do something," Salt muttered. "But what?"
"I know!" Penny exclaimed. "I'll telephone Dad and have him come hereright away with Major Bryan!"
"Good!" approved Salt. "I'll stay here and hold the fort while youtelephone. Tell your father to step on the gas, because we've got to movefast to queer Professor Bettenridge's game."