Standing beside the girl of “Mystery Isle,” Jack stared down at the five men and the jet plane in silence. “Here’s a ticklish situation,” he thought. He was glad he had established friendly relations with the natives. He and Stew, with only their sidearms, would be no match for those five men.

Jack’s amazement at this turn of affairs was great. He had been inclined to accept the men who first had the jet plane as Englishmen or Australians trying out a secret weapon. One thing was sure. This plane was no haphazard affair built from parts of other planes. It was brand-new and had been created in some up-to-date factory. There were little points about it that seemed to say, “Made in America,” but if it had been, how had these fellows gotten hold of it? It was a priceless possession, Jack was sure of that, for he had seen it perform. He’d seen many types of planes climb toward the stratosphere, but none had become a speck in the upper air as quickly as this one.
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“I’d like to get my hands on it,” he whispered to the girl.

“Wouldn’t you, though!” she whispered back.

Then the tall man nearest the jet plane did what to Jack seemed a strange thing. After lighting a large gas lantern that spread a white circle of light all about him, he climbed to the plane’s fuselage, threw back the canopies, hung the lantern on a pole propped against the inside of the cockpit, and then began tinkering with the controls.

“He certainly isn’t afraid,” Jack whispered to the girl. “Working in a flood of light on a strange island. What an easy mark he would make!”

“Perhaps he does not know you are on the island,” she returned.

“Wouldn’t those other men tell him?” he wondered.

“Who knows?” The girl’s words gave him the impression that she knew more than she cared to tell. “The Germans are not afraid of natives,” she went on. “Besides, they have machine guns.”

“On the plane?” Jack looked closely at the plane.

“Yes, two. I have seen them.”
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Jack unslung his binoculars. They brought the plane and the men closer to him. A look of intense concentration came over the boy’s face. He watched every move the man on the plane made, studied and memorized the instruments on the board, noted that they were fewer than on most planes, then gave his attention to the controls.

As if conscious of the boy’s intense interest, the man threw on the power. The motor squealed. A fine, misty smoke half hid the plane. The man threw off the power. The mist drifted away.

“That plane has no propeller,” Jack whispered, half to himself and half to the girl.

“No,” she agreed.

“It’s run by jets going out from the back,” he went on. “If you held a large balloon before you and it exploded, it would push you over. That plane works something like that. The Italians tried it. Their jet went straight back out of the fuselage. It ran the plane, but took too much fuel. This one takes air from the sky into a large compressor. When it is under high pressure it is mixed in a chamber with explosive gas from kerosene. This mixture is ignited under terrific pressure, then carried round a right-angle bend and blown through fans that somehow give it a lot more power.”

The girl was silent. Did she understand? He wondered.
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But now the man in the cockpit was ready for one more move. Once again he set the motor howling. This time however he released the brakes, dropped his lantern into the cockpit, touched the accelerator, and went gliding away into the night.

Jack had watched his every move. “That,” he whispered, “is about the easiest flying plane in the world. I could fly it right now.”

“So could—” The girl stopped, then added, “Yes, yes, I am sure you could.”

“I will, too,” Jack told himself, but did not say it aloud. No use telling too much.

They listened to the plane until its strange wail faded into nothing.

“He’s gone,” the girl said, half rising.

“I think he will be back,” Jack said, remaining in his place. “I want to find out all I can,” he added. The girl settled back in her place.

“That’s the fastest plane in the world,” Jack whispered. “I have seen it take off in daylight. In th............