When Jane, Maddie, and Michael, the children of the wealthy and uptight Banks family, are faced with the prospect of a new nanny, they are pleasantly surprised by the arrival of the magical Mary Poppins and her sister Martha. Embarking on a series of fantastical adventures with Mary, Martha, and their Cockney performer friend, Bert, and his crush, Pippa Banks, the siblings try to pass on some of their nanny's sunny attitude to their preoccupied parents.