12-year-old Martha Jane and her family are headed West in search of a better life in 1863 America. When her father gets injured, she learns to drive their family`s large covered wagon train and takes care of her siblings. She dresses as a boy and is often outspoken and bold, which rubs certain people in the community the wrong way. When Abraham, the convoy`s leader, accuses her of stealing, she sets out to prove her innocence and while doing so, discovers herself and a world that confirms her unique personality.