Two orphaned peasant children discover a mysterious pouch, the contents of which lead them to the majestic Castle Corona, where their lives may be transformed forever.

Mary, Johnny, and Lizzie Marston, and other children traveling on the Orphan Train from New York City, share hopes for their futures in good, loving homes in the American West.

When Alfredo, a twelve-year-old choir boy in eighteenth-century Italy, loses his family in a fire, he goes to live with Uncle Giorgio, who he discovers is a sorcerer in control of the fires of Mt. Etna with sinister plans for his nephew.

Orphan Catherine "Cat" Royal, living at the Drury Lane Theater in 1790s London, tries to find the "diamond" supposedly hidden in the theater, which unmasks a treasonous political cartoonist, and involves her in the street gangs of Covent Garden and the world of nobility.