“We’re not so helpless, Mac,” said Benson. “Nellie—”
“Finished,” said Nellie, standing up and shedding rope loops. “I’ve hacked my wrists to bits, though.”
The thing that had thudded into the wood between her and Rosabel before Benson’s capture had been The Avenger’s throwing knife, Ike.
Nellie had been sawing awkwardly at her bonds ever since. Now she was free.
She cut the loops from around Benson. The gray fox of a man trod on the burning rope and extinguished the flame, then loosed Smitty and Mac, Rosabel and Josh.
“We’re all right,” said Josh in a troubled tone. “But down in Chicago some unnamed building will fall—”
“No,” said The Avenger. “It won’t.”
They stared at him.
“They have very carefully built up the fear, in Chicago, of invasion from the air by some secret enemy,” Benson explained. “They have gone to great lengths to build up that terror. And in doing so, they have gone to great lengths — to plot their own destruction.” He stood before them, tautly erect, not a big man, yet seeming to fill the place. His death-white face was turned toward the point in the horizon toward the plane had set her nose.
The gang stared out through the invisible cabin walls as the mystery plane soared, at nine thousand feet, over the twinkling lights of South Chicago. It was about ten, now. The lake was a sheet of silver in the moonlight.
The skywalker!
Only there were eight skywalkers, now. Carlisle, and Darcey, and six gunmen. Of the six, one had Mike’s .22 slug in his shoulder and was sweating and swearing with pain. Another was still unconscious from having been so expertly creased by Mike’s little leaden pea.
“Will a man be standing by in the cruiser in the center of the lake to pick us up after we land and sink the plane?” Darcey asked nervously.
“Of course,” said Carlisle.
The sleek young killer was composed. Darcey was not. This was his first time aboard the special craft that had, at his orders, flown and destroyed five times before. He was very nervous. Yet he’d had to stick with the plane till it was finally destroyed, for his own protection.
“What’s the building we get this time?” Carlisle said, as the plane droned over the southern part of Chicago proper, with the tall buildings of the Loop just ahead.
“The Insurance Exchange,” said Darcey, dabbing at his moist forehead. “That’s one of the buildings in which both Catawbi steel and regular steel were used. It will, once more, show the superiority of Catawbi metal.”
“How is it,” said Carlisle curiously, “that this little vibrating dingbat can pick ’em so fine? Steel’s steel, I should think. Why isn’t Catawbi steel disintegrated?”
“I don’t think even the Gant brothers quite knew,” Darcey said. “There is a slight trace of chromium in Catawbi ore, and that seems to make the metal respond to a little different pitch of the vibrator. That’s all they could say about it.”
“Whatever makes the difference, it’s lucky for us—” Carlisle started to say. Then he pointed through the cabin wall. “They’ve heard us down below. Look! Four army planes. That’s a laugh — to see ’em circling around hunting us, and not seeing us — when all the time we’re right under their noses.”
“It may be humorous to you, but I don’t like it,” Darcey said, wiping more moisture from his clammy forehead. “Here! Set the vibrator, direct it as the Insurance Exchange, and let’s get through and away.”
Carlisle had handled the little thing before. The second, and most revolutionary, of the Gant brothers’ discoveries.
There was a black metal case, looking about the size of a small portable radio. In one side there was a screened circle, like that which conceals a radio loudspeaker. Inside the case there was a maze of fine antennae and delicate diaphragms, and two amplifying tubes. The contraption was hooked to a small generator geared to the plane motor, and that was all Carlisle could tell you about it. Darcey always set the pitch of the thing before a job, after experimenting with whatever steel was to be knocked to bits.
The disintegrator was all set now. Carlisle aimed a long, narrow cone so that its point was directly on the big Insurance Exchange Building, and snapped the little switch. There was a soft hum, raising rapidly in tone till it tore at the eardrums, then going up beyond the range of audibility.
“Hey!” said one of the men suddenly. “Them Army planes! Looks like they were coming right for us. As if they could see us!”
“Nonsense,” said Darcey, voice shaking but sure. “We are invisible.”
Carlisle said, “We’ll cut the motor for a few minutes, though. After all we can be heard, if not seen.”
They were hearing the drone down in the city. Hundreds of thousands of people were staring skyward. They saw the Army planes, but that was all. And none of them accounted for the eerie droning.
People shook their fists at the sky in agonized but futile rage. The enemy up there! If only it could be seen—
“Boss,” said one of the men, voice uncertain, “those planes are still comin’ right for us, even with the motor cut off—”
“So careful, they were, to build up that horror of an enemy invasion,” Benson was saying as all of them went out of the ferry to the blue sedan so generously left for them by Darcey’s overplayed plotting. “So successful, that under cover, Chicago is almost in a state of military rule. There are nine anti-aircraft guns of the latest type concealed in strategic spots through the city. And there are four of the fastest army battle planes ready to take off the instant detectors hear the droning noise. All training their deadly forces on the sky, waiting for the skywalker.”
“But what good will that do,” said Mac gloomily, “if nobody can see the plane?” The dour Scot, freed from death, was his pessimistic self again, sure that everything would go dead wrong in this worst possible of worlds—
The Glassite plane had wheeled from the strangely purposeful drive of the four fast army ships. The vibrator cone was no longer centered on the doomed building because of the maneuver.
“Swing it back,” ordered Darcey.
“Something’s gone wrong,” retorted Carlisle, eyes narrowed and venomous instead of deceptively calm and sunny. He countermanded Darcey’s order to the pilot. “Beat it! Out over the lake. The hell with the Insurance Exchange.”
“Carlisle — I’m giving the orders around here—”
“Look!” screamed the man with the wounded shoulder suddenly, glaring with horror in his eyes at the cabin wall.
That wall was glistening a little with reflected moonlight.
“That stuff you dipped the plane into!” the man yelled—“something’s gone wrong with it!”
“If the plane couldn’t be seen,” The Avenger replied to Mac, “the guns and army planes would be useless, of course. But Darcey’s plane, you see, isn’t going to remain invisible.”
“The barium stearate—” began Mac.
“The barium stearate,” said Benson, paralyzed lips barely moving in his white, dead face, “is adulterated. There was a small can of aviation gasoline near that drum. Probably to prime the diesel generator when they wanted to start it. I poured it into the barium stearate. It’s highly volatile stuff. It permeated the contents of the drum in a few seconds. This time the coating on that plane will dry and crack off in about a third of the time it usually takes.”
The terrified men in the Glassite plane saw a red spot burst in the city below them, heard a boom an instant later, and then felt the ship bob and twist in a gigantic rush of air.