Martha Tom, a Choctaw girl, crosses the Bok Chitto river to harvest blackberries knowing full well that the other side is controlled by a Mississippi slave-owning plantation, and if she were captured would become a slave herself. One day she befriends a young slave boy named Lil Mo who tells Martha that his family is about to be sold. Martha decides to help the family reach freedom and shows them how to cross the river. As the new family settles in the Choctaw town, sovereign by law, Lil Mo eagerly adapts, even meeting people with magical powers in the tribe, but also facing the dangers of the plantation's henchmen and a supernatural owl.