Grace Kelly was swept away when the handsome Prince Rainier, a man she barely knew, asked for her hand in marriage. After a series of relationships with married co-stars she was exhausted by the showbusiness lifestyle. If she married Rainier she would be more than just a movie star, she would be Her Serene Highness Princess Grace. Trapped in a fairytale of her own making, Grace was forced to make sacrifices that cut deeply into the core of who she was as a woman, surrendering her desires and ambitions for her spouse and her children. Grace and Rainier may have been royalty but they were also husband and wife, and parents - and, as such, just as vulnerable to the conflicts that can contaminate any household.

Drawing upon hundreds of exclusive interviews with family and friends, Once Upon a Time portrays its subjects with passion and sympathy, revealing Grace, Rainier, Caroline, Albert and Stephanie in ways both startling and compelling.