In spite of his steady nerves von Gobendorff's pulse quickened as the train came to a standstill on the centre of the lofty bridge. As he expected, the guard's attention was directed towards the signal set at danger. What was better still, the man alighted and walked along the permanent way.
The spy waited until he saw the guard returning. Five minutes had almost elapsed, but the signal had not dropped. Von Gobendorff was confronted by two alternatives: either to set the fuse in action and drop the explosive under the carriage before the guard returned, or else wait until the line was reported clear. He chose the former, relying implicitly upon his assistant's ability to lower the signal-arm.
Therein he made a grievous error, for the bolt, in being released from the operating rods of the signal, took it into its head to jerk itself out of the man's grasp, rolling down the embankment and choosing a secure retreat under the roots of a thick thorn-bush. The wrench which von Gobendorff's accomplice employed was too massive to be used as a temporary bolt, and in the absence of anything suitable it was impossible to pull down the arm to the safety position. The train beginning to move towards the fellow's scene of action warned him that it was unhealthy to linger longer, so taking to his heels he bolted.
Meanwhile the spy cautiously lowered the explosive out of the window, intending to swing it under the carriage, but forgetting that the dog's chain was padlocked round his own wrist von Gobendorff was unpleasantly surprised when the St. Bernard shook his massive head. The sudden jolt had the result of jerking the cord out of the spy's hand, and the leather case dropped upon the permanent way in full view of the occupants of the two adjoining carriages.
Von Gobendorff made no effort to retrieve his dangerous property. It was high time that he put a safe distance between him and the explosive, for the fuse had now been active for two minutes and the signal-arm still remained at danger.
Uttering maledictions upon himself for not having unlocked the dog's chain from his wrist the spy drew the key from his pocket. To his dismay the key failed to open the padlock, while an attempt to unfasten the rusty spring-hook that fastened the chain to the animal's collar was equally fruitless.
Once again the Teutonic love of detail had over-reached itself. Von Gobendorff had arranged everything to the minutest point, but there was a slight flaw in the operations and it led to failure.
Followed by the St. Bernard the spy leapt from the van and, taking advantage of the fact that the attention of the spectators at the window was centred upon the still obstinately fixed signal, was soon lost in the drifting mist that, fortunately for him, was rising over the eastern end of the bridge.
Knowing that there was a sentry posted on the embankment von Gobendorff advanced boldly, trusting to his disguise to enable him to pass. In this he was quite successful, for the man, on seeing the "Brass Hat" approach, stood still to the salute, the pseudo major returning the compliment in correct military style.
Once clear of the sentry von Gobendorff scrambled down the embankment and made towards the well-wooded country at high speed. With luck he hoped to cover half a mile before the expected explosion occurred; even then his margin of safety was perilously small.