the door of the box swung
open.

Inside was a complete radio receiving set, with vacuum tube detector and
batteries in perfect working order. Between the roots of the tree an
iron pipe had been driven into the earth to act as a ground. The antenna
was strung from top to bottom of the tree on the side away from the
path, and there was nothing to differentiate the box from an ordinary
wire telephone set, except that it was slightly larger. There were a
number of regular wire telephones scattered throughout the woods, to aid
in fighting forest fires, so that anybody traveling along the path would
have been unlikely to give this outfit more than a passing glance, if
they noticed it at all. Had the radio boys not chanced to see the
black-moustached man listening, with wireless headphones over his ears,
the fact that the box contained a wireless receiving outfit might never
have been discovered.

Brandon and Bob went carefully over every article of the equipment. They
were on the lookout for another notebook such as the boys had found in
the cabin, but there was nothing of the kind in the box. When they were
satisfied of this, Mr. Brandon carefully replaced everything as he had
found it, and snapped the lock shut.

"So much for that!" he exclaimed. "Now, let's get hold of the others and
we'll see what that mysterious cabin looks like."

Joe and Herb and Jimmy were soon recalled from their sentry duty, and
all set out along the path to the cabin. When they got close to the
clearing the three sentries were again posted, while Bob and the
inspector made a detour through the woods so as to approach the cabin on
the side away from the path, where there was little likelihood of those
inside keeping a lookout. Very cautiously they advanced from the
concealment of the woods, Frank Brandon with his right hand on the butt
of a deadly looking automatic pistol. They crept close to the wall of
the cabin, and listened intently for some sign of life within.

That there was at least one man in the cabin, and that he was still
sleeping, soon became evident, for they heard the heavy breathing of one
sound asleep. Mr. Brandon cautiously raised himself as high as the
window, and peered within. From this position he could not see the
sleeper, however, and he and Bob moved silently to the other side of the
shack. From there they commanded a good view of the interior, and could
plainly see the sleeping man, who was the same whom the boys had f