1863, United States of America. After 12-year-old Martha Jane’s father is hurt in a serious accident, she takes charge of her siblings and learns to drive the family wagon. Utterly practical and bold, Martha Jane dresses as a boy and becomes increasingly troublesome for the community due to her outspoken braveness. When the leader of the convoy wrongly accuses her of theft, she runs away to find proof of her innocence. In the Wild, she discovers herself and a world which shapes her and confirms her unique personality, revealing the mythical and slightly mysterious Calamity Jane.