rritt.

"I scarcely think so," was the rejoinder; "in fact, I have a pretty good
idea where he is bound for."

"And where may that be?"

"The place in which he lay this afternoon to read those signals from the
distant island. Depend upon it, he is going to meet the men who
manipulated that flag!"

"By hooky! That's so, Rob. What a mind you have for figuring out things!
Of course, it's plain enough now that he is betraying Mr. Barr by giving
drawings and plans of the submarine to Mr. Barr's enemies, but I didn't
think he'd take so bold a method."

"There's nothing very bold about it," retorted Rob. "He is a trusted
man, and has been given every opportunity to be dishonest, if it so
suits him."

"I guess that's right; but it's our duty to thwart him."

"You just bet it is, and we'll do it, too, if it's possible. See, there
he goes over the top of that sand dune. I could see his figure
silhouetted against the sky. I reckon it's safe now to take after him."

"All right, you say when."

"I'll give the word right here. Silently, now; remember he is on the
outlook for some interference with his plans, and a false move may spoil
everything."

"Don't worry about me. A first class Scout should be able to carry
through a simple little thing like this."

"Don't be too sure it's simple," admonished Rob, as they silently rose
from their crouching postures and took after the vague shadow; "this
thing may turn out to be bigger than we thought."

"Have you laid any plans as to what you will do if we do apprehend him
in the act of transferring the plans to Mr. Barr's enemies?"

"Not yet. There's no use crossing a bridge till you come to it."

Through the night the boys pursued their quarry as silently as two
snakes. At times they lost sight of him, but always his figure would
loom up against the star-sprinkled sky as he topped a sand dune. At
length they saw him pause and light the lantern, which he had used in
the shed, and which he still carried.

This done, he swung the light twice across his body, after the fashion
of a brakeman signalling a train to come ahead.

Instantly, out of the darkness, flashed an answering beacon--a red
light. The boys clasped each other's arms. That they were on the brink
of an exciting adventure they did not doubt. But in each lad's heart was
a firm resolve that, come what might, they would do their duty by Uncle
Sam.

"Was that red light shown from the other island?" whispered Merrit