Through an heirloom music box, Leo, a serious, responsible boy, and his badly-behaved cousin Mimi enter the magical world of Rondo to rescue Mimi's dog from a sorceress, who wishes to exchange him for the key that allows free travel between worlds.

Jessie returns to the magical world where her grandmother was born, where she deals with some griffins, dances with fairies, and borrows something to help her dance in her school concert.

Sonia, Rye, and his brothers have survived the perils behind the golden and silver doors, but Weld is still under threat from the skimmers, and the companions must pass through the ancient wooden door in a last, desperate effort to save their world.