Ambrose Gwinnett Bierce 
A Horseman In the Sky [EPUB ebook] 

First published in the San Francisco Examiner in 1889, Ambrose Bierce’s 'A Horseman In the Sky’, uses suspense and dreamlike imagery to help describe an unusual wartime episode. Set during the Civil War, a lookout in the Union army sees a mounted confederate spy across the river. Realizing the spy is his own father, the soldier faces a terrible ethical dilemma.