Mary Stuart's (Saoirse Ronan's) attempt to overthrow her cousin Elizabeth I (Margot Robbie), Queen of England, finds her condemned to years of imprisonment before facing execution.

A few decades after her original visit, Mary Poppins, the magical nanny, returns to help the Banks siblings and Michael's children through a difficult time in their lives.

Newlyweds, reluctantly decide to give ethical non-monogamy a try as their lives get increasingly complicated.