very little; but that
the secret of the whole affair was at the mouth of the Thames; that that
was where we were heading for when we were captured."

"And did you give him some kind of a hint as to the nature of the
mystery?"

Jack smiled.

"Well, yes," he said. "I told him he would find some queer explosives
there and a large number of swift torpedo boat destroyers, equipped with
submarine nets. I told him that these made nightly raids into the
Channel and the North Sea and thus disposed of the German submarines."

"And he believed it?"

"He seemed to. But that was the best I could do on short notice and
knowing no more than I do of the matter."

"Well, it wasn't so bad," grinned Frank.

"I flatter myself that it could have been worse," returned Jack
modestly.

They fell into a long silence, which was suddenly broken by Frank, who
exclaimed anxiously:

"Say! Do you suppose that could have been a trap?"

"Trap?" repeated Jack. "What do you mean?"

"I mean, do you think Lord Hastings or some of the other British
officers sent that man here simply to get evidence against us?"

"By Jove!" exclaimed Jack. "I never thought of that. Whew! Maybe I have
gotten us into worse trouble than ever."

"If it was a trap, I guess you have," returned Frank glumly. "Yes, it
was a good job you did, I don't think."

"Wait a minute, though," said Jack. "If it were a trap, it would be
plainly evident we didn't know what we were talking about. That should
be enough to let us out."

"Unless they believe we smelled a mouse and acted accordingly," returned
Frank.

"Oh, well," said Jack, "there is no use worrying about it. We'll have to
take what comes and that's all there is about it. Now, I'm going to rest
a bit. When they come in, wake me up."

He leaned back in his chair and closed his eyes; and in the meantime
Frank continued to turn events over in his mind.

Half an hour later Lord Hastings, the man who had led the party that
captured the boys, a figure attired in the uniform of a colonel of
infantry, and several others entered the room. The uniformed man Frank
immediately took to be Colonel Masterson, and he was right. Frank nudged
Jack and the latter opened his eyes. Then both boys got to their feet.

"So these are the German spies, eh?" said Colonel Masterson.

"That's not true," declared Frank hotly. "We are no more spies than you
are."

"So?" said the colonel insinuatingly. "Then how does it happen you hold