In 1939 London, Miss Guinevere Pettigrew is a middle-aged governess who finds herself once again unfairly dismissed from her job. Now she must seize the day if she wants a job. She does this by intercepting an employment assignment outside of her comfort level as social secretary. Arriving at a penthouse apartment for the interview, Miss Pettigrew is catapulted into the glamorous world and dizzying social whirl of an American actress and singer, Delysia...

In an effort to give their younger brother, Norman a project to keep him busy now that he has joined the family publishing house, the older Warne brothers agree to publish Miss Beatrix Potter's first children's book. They don't expect the book to sell well, but they need to keep Norman busy. As a single woman living in Edwardian London, Beatrix suspects this endeavor may provide her with a small measure of freedom. But she also has very specific ideas...