such friendly conversation with another man who is under suspicion?"

Frank's heart sank. So it had been a trap, after all.

"I can explain that, sir," said the boy, turning to Lord Hastings.

"I have no doubt of that," was the reply. "The question is, can you
explain it satisfactorily?"

"Yes, sir, we can," interrupted Jack.

Here Colonel Masterson took a hand again. He spoke to Lord Hastings.

"What shall we do with them?" he asked.

"That, colonel, is for you to decide," was Lord Hastings' reply.

"Do you think it necessary to call a court martial?" continued the
colonel.

"In view of the evidence we have, I should say not," returned Lord
Hastings.

"And still," said Colonel Masterson, half to himself, "it seems to me
that every man should be given a chance."

In the minds of the two boys now there was not the slightest doubt that
they were in as perilous a situation as they had ever faced.

"Lord Hastings," said Jack quietly, "I assure you you are all mistaken.
However, we shall protest our innocence no longer, for I see it would be
useless."

And then the two lads were treated to one of the surprises of their
lives. Lord Hastings' stern expression gave way to a smile, and he
strode quickly toward them and extended a hand to each.

"Surely," he said, "you didn't think I doubted you."

The lads were too stunned to say a word.

"I just wanted to teach you a little lesson," continued Lord Hastings.
"In the future, perhaps you will neither fall short nor go beyond your
orders. I ordered you to Gravesend. You should not have gone beyond."

"But Davis, sir?" exclaimed Frank.

"As long as you were here, apparently prisoners," was the reply, "I
simply used you to advantage. Davis is a German spy."

CHAPTER IV.

STRANGE WARFARE.

It was the following night.

Clad in heavy oilskins, Frank and Jack stood in the bow of the large,
high-powered motorboat as it sped down the Thames in the darkness. Not a
light was visible anywhere and it was impossible to see a yard ahead.
But in spite of this, the boat fairly flew over the water; for the
strong hand of Lord Hastings was on the wheel and there was not a spot
in the river with which he was not familiar.

"Whew!" said Jack, as he turned about to shield his face from the icy
spray. "This is what I call taking a long chance, if you ask me."

"I should say so," replied Frank, raising his voice to a shout to make
himself heard above the sound of th