Who Goes There (Historical Novel)

This is a story of a young man from New England with a specific brain condition that causes him to lose memory every once in a while. He has been spending every winter in the South Carolina trying to heal, and learning about the customs and tradition of the South. His knowledge about the South qualifies him to do a spy work for the Union, but his brain plays a trick on him once again. While in a Confederate uniform, he gets amnesia and ends up fighting for the South.