When nine-year-old Sarah Smith fetches potatoes from the shed, she hears an unusual noise and senses something is different. Somewhat apprehensive, she returns to the shed later and realizes it isn't a what in the shed but a who. Sarah knows she should tell her parents, especially when she learns a group of men are searching for a missing soldier, but she decides to leave some food for the stranger and finds her kindness returned in an unusual way.

The Exchange, a picture book for children, shares a story about the Civil War, a war that divided communities and even families. In the midst of these tensions, Sarah must decide what to do when she discovers someone is hiding on her family's farm.