Below it mighty crimson flashes leaped from the ground, and through the clatter of his motor Gerry heard the detonation of tremendous, thunderous charges. Now black spots of smoke floated before the flying specks, and from the ground guns spat fiery into action--German anti-aircraft guns replying to aerial torpedoes dropped from the sky. Others besides the officer prisoners of Villinstein and the German cadets of the nearby airdrome had waited for the moon that night. Allied pilots also had waited; and now, with the moon to favor and guide them, they had come to attack the chemical works and the munition factories of Mannheim! An allied air raid was on that night! CHAPTER XXI: THE RAID ON THE SCHLOSS Gerry’s feet thrust on the rudder bar, swinging his machine to meet them, while hot rills ran through his limbs, warming him against the chill of the night flight above the clouds. He had thought of the frontier as a hundred and fifty miles away--two hours’ flight at best in this slow, heavy training “bus”--but here his friends were bringing it to him. His excitement prevented him from realizing instantly that to his friends he must appear an enemy--a black-crossed Hun-bird flying to fight them. A covey of German pursuit planes, flushed up from some airdrome near the raided city, swooped upward in front of Gerry, climbing for the advantage of altitude before starting their attack upon the raiders. Gerry could see them clearly--triplane Fokkers mostly, of the swiftest, best-climbing, and best-armed type. Some of them saw him, but saw, too, that his machine was German. Probably the pilots wondered what that old “bus” was doing there, but no one investigated, while Gerry flew on. The clouds had quite cleared below, but the city of Mannheim, speckled with lights a few minutes before, lay dark except where the great crimson bursts of the allied torpedoes erupted; where flames fanned from roofs of burning buildings; where the scintillant points of searchlights glared into the sky. Rockets streaked above the black city; shells flared and flaked in the air; and the glory of battle grasped Gerry. Grasped O’Malley, too. He patted his machine gun and turned about in his seat, appealing to Gerry. Above them the Fokkers and the other machines of the German defense were diving and engaging the raiders; a light caught the under wings of a plane and showed Gerry the tricolor circles of the allies. Before it sparks streaked--the illuminated tracer bullets streaming from the machine guns; and toward it, beyond it--now through it--other sparks streaked back. These were the tracer bullets of the German who was attacking; and Gerry, jerking back his elevator, tried to climb; but the big, lumbering training “bus” responded only slowly.