When Philip Van Doren Stern passed away in 1984, his New York Times obituary eulogized him as “a historian, novelist and editor who was widely respected by scholars for his authoritative books on the Civil War era.” But while Stern authored a number of historical titles – including “They Were There: The Civil War in Action as Seen by Its Combat Artists,” “Secret Missions of the Civil War,” and “An End to Valor: The Last Days of the Civil War” – his most notable work was a short story that had nothing whatsoever to do with the Civil War. It...