owever, we had discovered the obscure spot where the secret
trials were in progress.

"I knew from the first that the tests must be in progress in this
district," Ray said, "for a month ago that motor engineer in Grantown of
whom you hired your cycle made a small part of a new motor for a man who
was a stranger. The part was broken, and the stranger ordered another to
be made. I learnt that the first night we were in Grantown."

He resolved to spend that night at Grantown, therefore we dined
together, and when we rose from table he went to his room in order to
obtain his pipe.

[Illustration: THE NEW BRITISH ARMY AEROPLANE: ROUGH SKETCH DRAWN BY
LIEUT. KARL STRAUS, OF THE GERMAN SECRET SERVICE.]

Ten minutes later he returned, saying:

"Just come with me for a moment, Jack."

I rose and followed.

We ascended the stairs, and passing along the corridor he halted before
the door of No. 11 and tapped at it quietly.

It opened, and Smith stood upon the threshold.

"I wish to speak with you a moment," Ray said, facing him determinedly.

The man's face fell. We both entered, but so surprised was he that he
could utter no protest.

We saw that on the table beneath the lamp was spread a number of
photographs and papers.

He had been writing upon a sheet of foolscap and the writing was in
German.

"Yes," exclaimed Ray in a tone of satisfaction as he bent over to glance
at the first few lines. "I see. You report: 'The upper plane is somewhat
curved, with an----'"

"What's my business to do with you, pray?" the man asked defiantly in
excellent English.

"Well, your business has interested me greatly, Herr Straus," calmly
replied my companion, "and I congratulate you upon the ingenious method
by which you got a sight of the Kershaw aeroplane at an early hour this
morning. I was at Lochindorb with you--and rather cold waiting, wasn't
it?"

The man now recognised gave vent to a quick imprecation.

"I see you've just developed that photograph you took in secret as she
sailed within twenty yards of you! But I shall trouble you to give it
over to me, together with the rough sketch I see, and your written
description of our new military invention," he said, with mock
politeness.

"I don't know you--and I shall do nothing of the sort."

"I know you, Karl Straus, as a spy of Germany," exclaimed my friend,
with a grin. "Your reputation for ingenuity and cunning reached us from
France"; and snatching up the sheet of