Life in New York’s grim 19th century slums consists of hardship for the poor but honest Kelly clan. When widowed Mrs. Kelly feels that she is no longer capable of providing for her children, she sends them west on the Orphan Train, to be adopted by farm families.

Frances masquerades as a boy in order to be adopted with Petey, the brother she promised her mother she would protect. Since Frances and Petey are adopted by a couple with strong abolitionist sympathies, just days after her arrival on the farm, Frances ends up helping two runaway slaves on the Underground Railroad.