The warning was necessary. The motor-battering-ram was charging straight for the window. Promptly the chums backed away from the bars. Judging by the speed and momentum of the petrol-driven vehicle there was great danger of the car charging completely through the stone building.
The next instant there was a violent crash. Stone, mortar, iron bars, woodwork flew in all directions accompanied by clouds of dust, while rearing at an alarming angle upon the mound of debris was the car.
It was totally wrecked. The muzzle of the anti-aircraft gun, having caught in the overhanging masonry, had been wrenched from its mountings, tearing away the steel roof of the car and pinning the two gunners under the heavy metal. The petrol from the burst tanks 'was saturating everything within the limit of its flood, although, fortunately for Tressidar and his companion, the highly volatile spirit had not exploded. To add to the horrors of the scene bombs from the British seaplanes were still falling.
"Come along!" shouted Tressidar, bawling to make himself heard above the din.
"Right-oh," replied Fuller with alacrity.
The sub. had no definite plan. All he knew was that a path had been cleared for them through the formidable barriers. There was a chance—a very slight chance—of liberty, and they seized it.
Crawling over the pile of debris and edging between the upturned side of the car and the jagged wall, they gained the open space between the building and the military road behind the dunes.
Glancing cautiously right and left, the two chums made the discovery that the coast was clear. The gunners of the stationary quick-firers, ensconced in their armoured emplacements, were too busy with their work to look elsewhere. A mile or so down the road and proceeding away from the prison buildings were two armoured cars. Every soldier, not actually engaged in firing at the seaplanes, had returned to the shelter of the dug-outs and bomb-proof casemates. Three distinct and fiercely burning fires showed unmistakable proof that the work of destruction had succeeded.
Through the gap in the shattered fence Tressidar and Fuller made their way. The severed electric wires were spluttering viciously, emitting bright blue flashes as their ends writhed like snakes. The mastiffs were no longer in evidence. Terrified by the crash of the falling bombs, they had scurried for shelter. The sentinels, too, their dread of official punishment outweighed by the fear of death or maiming from the powerful bombs, had deserted their posts, but not before a corporal and two privates had been literally wiped out of existence.
Through drifts of acrid-smelling smoke the two fugitives hastened, until they gained the slight shelter afforded by a dip in the reed-grown dunes.