tting our heads into trouble recklessly. Bob's good sense
prompted him when he refrained from pushing up to that radio station
by himself. There is something sinister about this. That place is
isolated, there are no roads near it, nobody ever hikes along that
beach except us. How did the station ever come to be built? Why, the
material and supplies must have been brought by boat. They couldn't
have been transported overland very well."

"What shall we do, though, Jack?" asked Frank, impatiently. "You can't
reasonably expect to have a thing like this rubbed under our noses
without our going ahead and investigating."

There was so much plaintiveness in his voice, as of a child from whom
a toy was being withheld, that Bob and Jack both burst into laughter.
Then Jack sobered.

"Tell you what I think," he said. "It's only mid-afternoon. Let's get
out your plane, and take a look at this place from the air."

"I guess the old boat is working all right now," said Frank. "How
about it, Bob? You know we haven't been up for two or three weeks,
Jack. Bob's been tinkering with it. When I last saw him at work, he
seemed to have the engine entirely dismantled. Looked to me as if he
had enough parts for three planes. Did you get it together again,
Bob?"

"Yes," said Bob. "And she'll fly now, boy, believe me. Well, come on,"
he added, starting for the hangar, not far distant but out of sight
behind the sandhills.

The others followed.

CHAPTER II

A STRANGE AIRPLANE APPEARS

From the Hampton radio station to the hangar on the Temple estate
where Frank and Bob kept their plane was a short jaunt, and the ground
soon was covered. Then Bob unlocked the big double doors and rolled
them back, and the three trundled the plane out to the skidway where
Jack spun the propeller while Bob manipulated the controls. As the
machine got under way, Jack ran alongside and was helped in by Frank.

Out over the sandy landing field trundled the plane rising so quickly
that Bob nodded with satisfaction. The loving work he had put in on
the machine had not been wasted. It was in fine flying condition.

They were not far from the coast and in a very short time were flying
over the water, whereupon Bob made a sweep to the right and the plane
headed westward. The Atlantic rocked gently below, serene under a
smiling sun and with only the merest whisper of a breeze caressing it.
On the southern horizon a plume or two of smoke, only faintly
d