It was almost like looking for a needle in a bottle of hay. Even taking into consideration the superior speed of the Dromedary, the initial start obtained by the Hun (supposing that Derek's surmise proved to be correct) and a slight divergence of courses would result in the two aeroplanes being separated by miles of darkness. Still keenly on the alert, Derek held on, at the same time putting a tray of ammunition to each of the two Lewis guns, the heels of which were within a few inches of the pilot's face. "I've missed the beggar," declared Daventry, after continuing the phantom pursuit for nearly a quarter of an hour. "Hard lines if the fellow were a Boche. I'll give myself another five minutes----By smoke! now what's that?" Right ahead, but on a slightly-lower level, was something gaunt, indistinct, and moving. For a few seconds Derek could hardly credit his good fortune, thinking that in the stress and strain of the night-flight he was the victim of a hallucination. Another minute, however, removed all cause for doubt. It was a 'plane; more, it was a Boche, for the black crosses of infamy were discernible in the cold starlight. The Dromedary was rocking in the tail-stream of the Hun machine. Gently Derek brought his 'bus up, until it was flying in comparatively still air. Eighty yards away was the Boche, flying serenely in blissful ignorance of the fact that a British machine was literally sitting on its tail. Deliberately, and without the faintest compunction--for the night-raider had none when dropping his powerful bombs upon the civilian population of London and other cities and towns--Derek brought the sights of the right-hand gun to bear upon the back of the Hun pilot. A burst of vivid flashes, and the deed was done. The German machine dipped abruptly, and dropped into a spinning nose-dive, while a long trail of reddish flames, terminating in a cloud of fire-tinged smoke, told its own tale. The petrol-tank had taken fire, and the doom of the raider was sealed. No amount of trickery would avail. It was impossible for Fritz to attempt his now well-known spin in the hope of deluding his antagonist, and then, by flattening out, get clear away. The fire had "put the hat" on that, even if the pilot had not been killed outright by the hail of Lewis-gun bullets. "May as well see what happens," soliloquised Daventry. "So here goes!" Diving almost vertically, he followed the visible track of the crashing Hun. With his feet braced firmly against the rudder-bar, and his head and shoulders well back, Derek maintained the plunge, ready at the first inkling of danger to either loop or flatten out. In spite of the terrific pace, the flaring debris of the vanquished Gotha was falling even faster, followed by a galaxy of falling embers.