tly smuggled all the material up and built the three
planes right here," Carter went on. "I watched them putting on the
finishing touches and testing the guy-wires. There is a machine shop,
too, rigged up in one of those outbuildings. The thing that gets me is
how they got the engines here. All the planes are equipped with powerful
new engines."

"If there are traitors in the army and navy, why not in the aeroplane
factories, too?" suggested Fleck. "A spy in the shipping department
could easily change the label on even a Liberty motor intended for one
of Uncle Sam's flying fields. Even when it didn't turn up where and when
it was expected, it would take government red tape three months to find
out what had become of the missing motors."

"These machines"--said Jane suddenly, "they must be the 'wonder-workers'
old Mr. Hoff was always talking about."

"And that last advertisement we read," Dean reminded them, "announced
that the wonder-workers would be ready Friday. It looks as if we got
here not a minute too soon."

"You bet we didn't," said Carter. "Every one of those three planes is
fairly loaded down with big bombs, scores of them."

"To bomb New York," said Fleck soberly; "that's their plan. Zeppelins
for England, big guns to shell Paris, bombs from the air for New York.
It's part of their campaign to spread frightfulness, to terrorize the
world. Undoubtedly that is the reason Berlin sent Frederic Hoff over
here, to superintend the destruction of the metropolis. There have been
whispers for months and months that the city some day was to be bombed,
but we never were able to discover their origin."

"And not a single anti-aircraft gun or anything in the whole city to
stop them, is there?" cried Jane. "Wouldn't it be terrible?"

Fleck smiled grimly.

"Any foolhardy German who tries to bomb New York from the air has a big
surprise coming to him--a lot of big surprises. The war department may
not have been doing much advertising, but it has not been idle."

"Then we have some anti-aircraft guns!" cried Jane delightedly. "I never
heard anything about them."

"That would be telling government secrets," said Fleck, smiling
mysteriously, "but I'd just like to see them try it. I have sort of a
notion to let them start their bombing."

"Oh, no, we mustn't," Jane insisted. "We mustn't let those aeroplanes
ever start. Can't we do something right away to cripple them?"

"There's plenty of time," the chief assured he