ent--the German was
hardworking, thrifty, and a pattern of all the virtues.

One evening, however, a curious incident occurred.

Ray had run up to London, leaving me to watch the German's movements.
Klauber had returned to Mrs. Macdonald's about eight, but not until
nearly eleven did he come forth again, and then instead of taking his
usual road to Inverkeithing to meet the girl Robinson, he ascended the
hill and struck across the golf-course until he had gained its highest
point, which overlooked the waters of the Forth towards the sea.

So suddenly did he halt that I was compelled to throw myself into a
bunker some distance away to escape detection. Then, as I watched, I saw
him take from his pocket and light a small acetylene lamp, apparently a
bicycle-lamp, with a green glass. He then placed it in such a position
on the grass that it could be seen from far across the waters, and
lighting a cigarette, he waited.

The light on the Oxcars was flashing white and red, while from distant
Inchkeith streamed a white brilliance at regular intervals. But the
light of Heinrich Klauber was certainly a signal. To whom?

He remained there about half an hour, but whether he received any
answering signal I know not.

Next night and the next I went to the same spot, but he failed to put in
an appearance. Then, in order to report to Ray, I joined the morning
train from Perth to London.

On arrival at New Stone Buildings I telephoned to Bruton Street, but
Chapman, his valet, told me that his master had slept there only one
night, had received a visit from a respectably dressed middle-aged
woman, and had gone away--to an unknown destination. Therefore I waited
for a whole week in anxiety and suspense, until one morning I received a
wire from him, despatched from Kirkcaldy, urging me to join him at once
at the Station Hotel in Perth.

Next morning at nine o'clock I was seated on the side of his bed,
telling him of the incident of the lamp.

"Ah!" he exclaimed after a pause. "My surmises are slowly proving
correct, Jack. You must buy a bicycle-lamp down in the town and a piece
of green glass. To-night you must go there at the same hour and show a
similar light. The matter seems far more serious than I first expected.
The enemy is no doubt here, in our midst. Take this. It may be handy
before long," and he took from his kit-bag a new .32 Colt revolver.

By this, I saw that he had resolved upon some bold stroke.

That evening,