in the Bristol Channel and off the
south coast of Ireland.

A couple of slight incidents had served to put the cautious
Ramblethorne on his guard during his interview with von Ruhle in the
ruined chapel.

Although he verbally deprecated his subordinate's alarm when the lads
accidentally dislodged a stone from the tower, it was merely to disarm
possible eavesdroppers of any suspicion that their presence was
suspected.

The ability to control his feelings was one of the super-spy's chief
assets. Suspicion once aroused, he proceeded without the faintest sign
to investigate his surroundings. His keen eye soon lighted upon the
lads' sweaters. Then it was that an adjournment was suggested to Main
Beach Cove.

This was simply and solely a "blind", for on gaining the cover of the
boulder-strewn hillock the doctor communicated his suspicions to his
companion. The pair then crouched behind the rocks, whence they were
able to command a view of the tower.

It was not long before their enterprise met with success. They saw
Trefusis and his chum cautiously descend by means of the ivy; then,
directly the lads set out upon their ill-starred tracking expedition,
the Germans, as before related, succeeded in outflanking them and
effecting their capture.

"Time!" announced Ramblethorne, consulting his watch.

"Are these safe?" asked von Ruhle, stirring Vernon's unconscious form
with his foot.

"Quite; though, perhaps, to make sure I will give this youngster a
slight injection. Pity you hadn't held him with the double arm-lock
instead of cracking him over the head. Herr Kapitan Schwalbe won't
want to be troubled with a passenger with a swollen head."

Leaving their senseless victims in the cave, the two Germans again
ascended the hill to St. Mena's Chapel. As they breasted the summit,
they could see the fixed white light of Black Bull Head showing
momentarily brighter and brighter against the rapidly failing daylight.

Setting a prismatic compass in position upon the sill of one of the
glazeless windows, Ramblethorne took a careful bearing in a seaward
direction. This done, he pointed the projector of the signalling
apparatus in precisely the same direction, and threw a waterproofed
cloth over the instrument.

"Too early yet, von Ruhle," he remarked. "Nevertheless it is advisable
to fix our bearings while twilight lasts. A light might spell
disaster."

"A deucedly unpleasant night for such a task," grumbled von R