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.

After a banker's children lose their nanny due to her frustration with them, a change in the wind blows in a magical nanny who matches the children's qualifications, but not those of their very proper father. As Mary Poppins helps the children magically explore the world around them, their father grows increasingly disapproving of her methods, and he must eventually deal with his own distance from his children.