Mary Poppins returns to the Banks family in a rocket and involves the Banks children in more magical adventures including those with Peppermint Horses, the Marble Boy, and the Cat that Looked at the King.

When a thirteenth-century wizard confronts twenty-first century Boston while seeking his pet dragon, he is followed by a rival wizard and a very unhappy demon, but eleven-year-old Theodora Oglethorpe may hold the secret to setting everything right.

Mary Poppins comes back on the end of a kite string, stays with the Banks family for a while, and then disappears on a merry-go-round horse.