After marrying a successful Parisian writer known commonly as "Willy" (Dominic West), Sidonie-Gabrielle Colette (Keira Knightley) is transplanted from her childhood home in rural France to the intellectual and artistic splendor of Paris. Soon after, Willy convinces Colette to ghostwrite for him. She pens a semi-autobiographical novel about a witty and brazen country girl named Claudine, sparking a bestseller and a cultural sensation. After its success, Colette and Willy become the talk of Paris...

A film is being made of a story, set in 19th century England, about Charles, a biologist who's engaged to be married, but who falls in love with outcast Sarah, whose melancholy makes her leave him after a short, but passionate affair. Anna and Mike, who play the characters of Sarah and Charles, go, during the shooting of the film, through a relationship that runs parallel to that of their characters.