u come
from?"

Then, as Frank made a clutch for his ankle, he brushed him aside and
sat down on the sand:

"Say, listen, cut out the fooling. I've got something to tell you
fellows."

Bob was so plainly excited that his chums were impressed. Scrambling
up they seated themselves beside him.

"Fire away," said Jack.

"What would you say to my finding the tracks of a peg-legged man
coming up out of the sea, crossing the sands of Starfish Cove and
disappearing into the trees beyond there?"

The inlet which Bob thus referred to was some three miles distant,
with a patch of timber some twenty yards back from the water and a
ring of low sandhills behind the woods.

"A peg-legged man?" said Frank. "That certainly sounds piratical. Go
on. Your imagination is working well to-day."

"Did he arrive in a boat?" asked Jack.

Bob nodded.

"Yes. I found where the boat had been run up on the sand. But--he
didn't leave. The boat went away without him. He disappeared inland,
and there were no tracks marking his return."

Jack whistled.

"Whew. Did you follow?"

"Did I follow? Huh. You can just bet I did follow. And, say,
fellows----"

"What?"

"I know now where that strange interference in our radio receivers
comes from."

"Is that so?" demanded Jack, excitedly. "It was cutting up didoes just
a few minutes ago, just before you arrived. Had been for some time,
too."

"Well," said Bob, "that's not to be wondered at. For when I followed
Peg Leg's tracks through the trees I discovered a radio station tucked
away in a hollow behind the timber, with sandhills hiding it on the
landward side. I watched for a while from behind a tree, but couldn't
see anybody. Then I hustled here to tell you fellows about it."

Puzzled, the trio regarded each other in silence. Presently Jack
spoke.

"Look here, fellows. There's something queer about this. A mysterious
radio station, hidden away, that sends a continuous wave on a hitherto
unused wave length. This has been going on for a week. What does it
mean? Then there is this man, this Peg Leg, whom Bob discovers
arriving from the sea."

"Let's go together and investigate," cried Frank, jumping to his
feet.

"I'm with you," declared Bob, also arising. "I would have gone up to
the station and done that very thing, by myself, but--I don't
know--there was something about it all--something sinister."

"Wait a minute, you fellows," said Jack, also springing upright. "We
can't go pu