The Orphan Train saga begins in 1856 in New York City where Mrs. Kelly, a young widow, realizes that she cannot give her six children the life they deserve. Mrs. Kelly makes the ultimate sacrifice of love and sends them west on the orphan train to fred better lives with new families. The children, especially thirteen-year-old Frances Mary, feel an overwhelming sense of betrayal and abandonment.

Their arrival in St. Joseph, Missouri, separates the children not only from their mother, but from each other as well. One by one they are adopted by western families -- some looking for children to love, others only seeking cheap labor. Frances has promised Ma that she will look after Petey, her youngest brother, no matter what. When she masquerades as a boy, "Frankie's" adventures eventually involve her in the activities of the Underground Railroad. Will honoring Ma's request help Frances understand that splitting up the family was really her mother's act of love?