The Interlopers

From the text:

In a forest of mixed growth somewhere on the eastern spurs of the Carpathians, a man stood one winter night watching and listening, as though he waited for some beast of the woods to come within the range of his vision and, later, of his rifle. But the game for whose presence he kept so keen an outlook was none that figured in the sportsman’s calendar as lawful and proper for the chase; Ulrich von Gradwitz patrolled the dark forest in quest of a human enemy.