From his place of concealment Otto Oberfurst sat and waited while the lengthening shadows betokened the approach of another night. At frequent intervals he consulted his watch. It was almost identical with the one he had left in the double bottom of the "Pompey."
Occasionally he directed his attention to the dark brown ribbon that marked the position of the main road leading to Auldhaig, but his gaze was chiefly concentrated upon the land-locked harbour. The "Pompey," lying on the extreme west of the line of moorings, was plainly visible. To all outward appearances she looked to be the embodiment of armed security, protected as she was by triple lines of anti-submarine devices that barred the entrance to the firth. In addition to the numerous warships, ranging from large armoured cruisers down to the swift, well-armed craft of the destroyer flotilla, the harbour was protected by four distinct anti-aircraft batteries armed with the very latest type of guns. The positions of these concealed batteries the spy knew with startling accuracy. He also knew that a short distance inland from Auldhaig, and situated in a remote and naturally sheltered valley, was the important munition factory of Sauchieblair. Three times had German aircraft sought to discover the exact position of these immense works. On the last occasion bombs had missed the main cordite factory by two hundred yards; but that was more by good luck than good judgment, for never in the course of their flight over the Scottish coast had they been absolutely certain of their bearings.
Four o'clock. Otto Oberfurst, his hands shaking in spite of his strong nerve, awaited the result of his treacherous handiwork. Ten—twenty—thirty seconds passed, but still no terrific explosion that would rend the cruiser from stem to stern. A wave of horrible uncertainty swept over him. Perhaps suspicion had been aroused and the double bottom had been searched; or a flaw in the intricate mechanism of the timing-gear had prevented the deliberate catastrophe. In either case the failure would be of grave consequences to the German Secret Service plans. The actual proof that an attempt had been made to destroy a warship by internal explosion would make it advisable to discontinue activities in that direction. So long as the British attributed similar disasters to accident, well and good. They could set forth as many theories as they liked, provided that the real reason was known only to von Schenck and his associates.
Suddenly Oberfurst's cogitations were interrupted by the sight of a cloud of smoke leaping skywards from the cruiser. Four seconds later the muffled boom of the explosion was borne to his ears. He could see the vessel listing, but to his intense disappointment she showed no signs of being blown to pieces.
"Himmel!" he muttered. "It is not the magazine this time. I must have miscalculated its position. No matter, another English ship is out of action. Better luck next time!"
He waited until the "Pompey" had disappeared from view beneath the waters of Auldhaig Harbour, then, walking rapidly, he followed a mountain path leading away from the town.
Darkness had fallen when he arrived at a small stone cottage situated in a remote glen. With the ease of a man who was familiar with his surroundings, Oberfurst climbed the stile in the wall enclosing the garden, threaded his way along the winding path, and, avoiding an invisible obstruction in the form of an iron pig-trough, tapped softly upon the window-pane.
"Who's there?" inquired a high-pitched voice.
"All right, mother," replied the spy reassuringly.
Without further delay the door was unbarred and Oberfurst entered the cottage.