Carter's life is turned upside down when her dad, Major Mason of the Princess Protection Program - a secret organization that rescues princesses - brings Princess Rosalinda home to live with them. Princess Rosalinda's country has been taken over by a dictator and she must adopt the cover of normal American girl Rosie Gonzalez to protect her identity. Now it's up to Carter to help Rosie fit in, but that proves to be easier said than done when Rosie has trouble giving up her royal ways.