"Boom, boom--boom, boom, boom!"
The hollow, reverberating sound of five reports fell upon the listeners' ears.
"Ten miles off," declared the non-com., as calmly as if giving the range of a howitzer. "Good!"
Another flash, followed at a shorter interval by the crash of the exploding bomb told unmistakably that the raiders were approaching. The men felt like cheering. Even the prospect of being strafed by a British bomb did not cause them the slightest concern. In their blind faith they regarded a bomb as the key to unlock their prison doors.
Very faintly at first, then steadily increasing in volume, came the hum of many British aircraft.
"No Gothas this time!" exclaimed Peter, who, like the rest of the men, could distinguish with unfailing certainty the different "pitch" of the British and Hun machines.
"Here they are!" almost shouted Malcolm, pointing into the night.
He was not mistaken. Flying in perfect V-shaped formation, and at a low altitude that made the airmen more certain of hitting their objectives, were eleven biplanes standing out sharply against the star-lit sky.
"Crash! crash!! crash!!!"
Away on the left a battery of antis., the guns mounted on motor-lorries, opened a furious fire upon the rapidly-moving airmen. The air was thick with bursting shells, the flashes of which threw a lurid light upon the ground. The gunners were only a hundred yards or so from the barbed-wire enclosures.