Out of the Blue — Josh Lanyon

France, 1916. The Great War. High above the carnage in the trenches, British and German aces joust like knights of old for control of the skies. The strain and tension of living every day on the edge of death leads to dangerous choices and wild risks. When British ace Bat Bryant's past catches up with him, he strikes out in panic and kills the man threatening him with exposure. But there's a witness: the big, handsome American pilot Cowboy Cooper.

Cowboy, it seems, has his own ideas of rough justice.