Bonnie and Sylvia Green are opposites in many ways. While Bonnie is bubbly and daring and has grown up with every luxury she could wish for, Sylvia is a ladylike and timid orphan whose aunt can barely afford food and clothing. Despite their differences, when Sylvia comes from London to live in the country with Bonnie and her parents at Wiloughby Chase both girls are delighted with one another, but when Bonnie's parents embark on a sea voyage to cure Lady Green's health, a very menacing governess comes to take charge of the girls. Miss Slighcarp sends them away to a horrible boarding house run by another cruel woman, Mrs. Brisket. Bonnie's boldness and Sylvia's tenderness help them to fight back against their afflictions. Their friendships with the kindly servants of the Chase and the boy who lives in the wilderness on the grounds also aid them in their quest to escape from Miss Slighcarp and Mrs. Brisket.