Escape by Night — Laurie Myers

Ten-year-old Tommy and his sister Annie are intrigued by the new soldiers arriving in their Georgia town. Since the Civil War started, wounded men waiting to be treated at the local church-turned-hospital have been coming in by droves. When Tommy sees a soldier drop his notebook, he sends his dog, Samson, to fetch it. Tommy soon meets the soldier and is faced with the hardest decision he's ever had to make: whether or not he should help a Yankee escape to freedom.