Grace of Monaco is focused on former Hollywood star Grace Kelly's crisis of marriage and identity, during a dispute between Monaco's Prince Rainier III and France's Charles de Gaulle in 1962, as well as her considering a return to Hollywood to film Alfred Hitchcock's Marnie.

In 1962, several years after her departure from Hollywood in 1956, Hitchcock visits Princess Grace in Monaco with an invitation to return to Hollywood to star in his new film Marnie. The offer comes with a lucrative incentive of a million-dollar contract if she accepts his offer for the starring role. Princess Grace is intrigued by the offer. Her role as the wife of a head of state has been limited in scope and dealing mostly with charity work for hospitals and humanitarian efforts. She asks her husband for permission and he initially appears to be agreeable to her taking the role if she wants the part.