Twilight Patrol - Laurence Raphael Brothers - Bog

The year is 1917. War rages in Europe and beyond. Far, far, beyond.
Harry Tregeseal is a new pilot in the Royal Flying Corps. For Harry the roar of his biplane's engine, the thrilling rush of speed, and the beauty of the open skies make flying glorious. But after his first combat he's heartsick, feeling more a murderer than a soldier. He'd give anything to avoid having to kill again, but that isn't a choice he can make, not serving at the western front.
When Harry is assigned to a squadron serving in a magical otherworld he thinks his prayers have been answered. But war is still hell, even in Faerie. Under a black poisonous overcast an army of enthralled slaves marches on Harry's airfield. The squadron's machine guns are ready to fire, but Harry can't stand the thought of more innocent blood on his hands. Yet if the squadron is overrun, millions will die.