e receiving radius, this plane
was the boys' especial pride.

What was their dismay, therefore, when they rounded the shed from the
rear and found the great doors which they had left padlocked several
days before standing open and the interior empty. For several moments
they stood as if rooted to the ground, staring in stupefaction. Then
Bob groaned, and Frank echoed him.

"Gone."

"Gone."

Frank was the first to recover from his dismay and ran forward to look
at the broken padlock, dangling from one leaf of the great folding
doors. "Cut through with a file," he called excitedly to his chum.
"And this set of big bar locks above and below the padlock were cut
the same way."

"I always said we should have had one of those rolling iron screens,
fitting solidly into the ends of the side walls and rolling up into
the roof," groaned Bob, passing on into the interior. "But what's the
use locking the barn after the horse is stolen." Disconsolately he
moved around the interior of the shed, as if expecting to find
concealed somewhere the airplane which he could not yet bring himself
to believe had been stolen.

Suddenly he let out a whoop. "Frank, look at this."

"Great Scott, an Iron Cross," cried Frank, seizing the object held
out. A German Iron Cross it was. "And here you can see how this ribbon
frayed through and parted from the clasp," added Frank.

"Turn it over," said Bob. "If it's a real one given by the Kaiser it
will have the recipient's name on it."

Sure enough, there it was:

"Ober-Lieutenant Frederik von Arnheim."

And beneath was inscribed:

"Pour le merite."

"Great Scott, Bob," said Frank. "What do you make of this?"

"Some Hun officer stole our airplane," said Bob. "That's what I make
of it."

"But the war is over," protested Frank.

"Maybe it is," said Bob darkly. "But if that bird doesn't fly back
with our airplane I'll make war on Germany myself."

Despite his gloom, Frank grinned. He slapped big Bob on the back.
"Come on, old boy," he said. "No use hanging around here. We may as
well go back to the house and report the latest mystery."

"I wonder," said Bob, as they set out, "whether there is any
connection between the two--between this theft of our airplane and
that stuff yesterday."

It was Mr. Temple who was able to provide an answer to that question.
The boys found him up and dressed when they reached home, and himself
considerably excited over a telephone call from New York Ci