The German bird craft suddenly appeared over Dunkirk like a flock of gigantic sea gulls. Explosive missiles fell as fiery hail upon the town. The tocsin sounded in the high tower of Dunkirk church, and the blue and white flag of the town was run up. The roar of the fort guns, firing shrapnel, was heard, and all around the German fliers white puffs were bursting, as the pilots guided their machines in low-swooping spirals. In compliance with the snappy commands of Roque, Billy circled the seaplane to every point of observation vantage, while the secret agent viewed the action of the armored Aviatik biplanes, dashing here and there with the sun glinting on their steel sides. "Look there!" shouted Henri, rising and clutching a stay to preserve his balance. The air was clear, and the scene was open even to the naked eye. Billy, at the wheel, risked a glance sideways. A squadron of British aviators, encamped on the outskirts of Dunkirk, had taken the air to engage the raiders. One speedy biplane darted straight toward the German craft. Henri saw the aviator clutch the levers of his machine in one hand and with the other unsling a rifle, beginning fire at a German birdman below him. A half dozen armored aëroplanes of the raiding force swarmed in upon the daring Briton. His machine was peppered with lead, and it was apparent that the man had been wounded as he dipped toward the earth to evade the encircling Germans. Other English aviators swept into the whirling combat, and to the rescue of their wounded leader. The raiders turned toward the north, now being shrapnelled by anti-aircraft guns stationed along the coast. Roque pointed upwards, signalling for rapid ascent, and at six thousand feet the seaplane, with tremendous burst of speed, soon overhauled and outdistanced the slower warcraft, making a wide detour over the sea, thus avoiding the volleys of rifle shots from the Allies' infantry near Nieuport. Roque, looking at his watch, turned to Billy, just behind him, remarking: "That much in fifty minutes is not often recorded--of these things they shall sing on the Rhine." In Bremen the boys paid grateful tribute to rest after the strain and stress to which they had been put by their relentless taskmaster. "I feel," said Billy, "like the hump between my shoulders is going to be permanent, and I couldn't keep my elbows down to save my soul." "If I could only get the whirr out of my ears, I'd be satisfied," was Henri's complaint. It was not long, however, before the boys found relief from the kinks in their backs, and were ready and eager for the next move in their adventurous careers. Just around the corner from their hotel was the very café where they had the thrill of seeing Anglin's face in the mirror while they were dining there with Roque. "Wouldn't it be funny if Anglin were to bob up again while we are here?" "I think, Billy, that it would be a tragedy if Roque had any inkling of it."