Carter (Selena Gomez) is a small-town girl and total tomboy. She couldn't be more different from Rosalinda (Demi Lovato), a South American Princess from the country of Costa Luna. After Carter's father, an agent in the covert Princess Protection Program, rescues Rosalinda from a military takeover, the girls are thrown together as "cousins"...and that's when the worlds of royalty and roughing it collide. In an unexpected role reversal, "Rosie" learns how to act like an everyday girl and Carter finds her own inner princess. Once they discover what they have in common, they prove that best friends really are forever. It's now up to the two friends to devise a plan to take down Costa Luna's dictator and return Rosalinda to her rule.