glass. I caught the
glint of the sun on the lenses."

"Why should he want to be watching us?" demanded Hazelton.

"That's just what made me curious," replied Prescott. "As an army officer,
if this were a fort that I commanded in troublous times, I'd want to look
into any strange craft that I caught cruising lazily in the offing and
holding a marine glass on us."

"I wonder if that boat can be in the service of those who are annoying us?"
Tom muttered.

"It's an even chance that it is a 'hostile ship,'" Prescott suggested.
"You have a motor boat here. I'm inclined to think you ought to use it in
overhauling that suspicious craft. Of course you'd have no right unless
there was a police officer along. Can you get one?"

"The authorities in Blixton would send a policeman on request."

"Then send a messenger to request them to send over a policeman in
citizen's clothes," proposed Dick.

Tom promptly despatched Foreman Dill on that errand.

"Now don't let the men on the boat see that you're paying any more
attention," Prescott advised. "Leave it to me, and I'll contrive to keep
the boat and its people under observation without looking too plainly in
their direction."

In due time the plain clothes policeman arrived. He, the young engineers
and the army lieutenant boarded the "Morton," which put out from the
landing as though on a trip of inspection of the wall.

"Don't anyone look over at the sloop," Prescott urged. "I'll do the
watching. A fellow on that craft is holding the glasses on us right now.
Officer, do you demand the assistance of all present in any police duty
that may come up?"

"I do," replied the Blixton policeman, a man named Carnes, returning
Prescott's wink.

"All right, then," laughed Dick. "That demand makes policemen of us all.
Tom, you can turn, now, when ready, and put on full speed in going after
that craft."

Reade gave the order for full speed, then took the steering wheel himself.

"Guilty conscience!" laughed Prescott. "There's the sloop putting about at
once and heading away from us."

"They can't get away from us, in this light wind," chuckled the young chief
engineer.

A few minutes later the "Morton" came up within easy hailing distance of
the sloop, aboard which only one man now appeared.

"Sloop ahoy!" called the policeman. "What are you doing in these waters?"

"Looking for a good fishing ground," answered the dark-faced man at the
tiller.

"Then you're t