Set in 1886 America, two young Irish siblings Mary (9-year-old) and Tom (12-year-old) arrive on an ocean liner to the hustle and bustle of New York City. They made the long trip to meet their Uncle Niall and secure their inheritance. But when Uncle Niall, who resides in California, fails to meet them, they decide to try to find him. Nearly penniless, they stow away on the Transcontinental Railway, meeting danger at every turn, until they join forces with a young, handicapped boy and his Governess, Eleanor, in the hopes of making it to California.