The mystery of the six red lights was now no longer a mystery. To the sub.'s keen intelligence the whole thing was as clear as daylight. The lid of the tool-box at the rear of the car had been partly raised until it formed an angle of 135 degrees with the back of the body. The lid, being of burnished metal, served as a reflector, so that the three red lights appeared to be six in a straight vertical line.
And that line pointed in the direction of the Sauchieblair Munition Works.
"That will do," said a voice in German--a language of which Tressidar had more than a general knowledge. "We're right on the exact bearing. Call up Pfeiller and inform him that our position is fixed."
The fellow who had been engaged in manoeuvring the car stepped inside the coupé. The faint cackle of a low-powered wireless apparatus was faintly borne to the sub.'s ear.
"Pfeiller reports all right at his position," announced the man after a brief interval.
"Let us hope he is sure on the point," remarked the German with the compass.
"He is a careful man at that sort of work," said the other reassuringly. "Now comes the worst part of the business--the waiting. Himmel! I t is cold on these hills."
"If she picks up the coast lights without difficulty she ought to be here by eight o'clock," said his companion. "These English have already had warning. That is why they have turned out the lights. Can you imagine them, friend Otto, cowering in darkness, waiting for one of our incomparable Zeppelins to blow them to pieces? And there is not even a puny, so-called anti-aircraft gun nearer than Auldhaig."
Ronald Tressidar had heard enough. His first impulse was to retrace his steps quietly and make his way to Nedderburn to procure assistance. But upon further consideration he came to the conclusion that before the spies could be made prisoners the Zeppelin's work might be accomplished. Prompt measures were necessary.
Creeping away to a safe distance, the sub. removed his heavy great-coat. To have the unencumbered use of his limbs was essential to the work he proposed attempting.
Again he stalked the two Germans. Unheard and unseen he gained the remote side of the car, then working round the front he leapt upon the nearmost of the spies.