A princess whose country has been invaded goes into hiding in Louisiana, where she has to learn to act like an ordinary teenager. ## Personality Princess Rosalinda María Montoya Fiore is about to be crowned queen of the small nation of Costa Luna. General Magnus Kane, the dictator of a neighboring country, Costa Estrella, invades her palace with his agents during her coronation rehearsal and attempts to capture the royal family and take over the country. Major Joe Mason, an agent of the Princess Protection Program (P.P.P.), a secret organization funded by royal families that looks after endangered princesses, whisks her away to safety via helicopter. Kane's agents, however, succeed in capturing her widowed mother, Queen Sofía Fiore of Costa Luna. The Princess Protection Program hides Rosalinda in Joe's home in Lake Monroe, Louisiana, where she meets his teenage daughter, Carter Mason. Carter is an insecure tomboy who works at the family bait shop and dreams of going to the homecoming dance with her crush, Donny, although her classmate, Ed, secretly has a crush on her. Rosalinda poses as "Rosie Gonzalez", Carter's cousin from Iowa. Though Carter initially treats her with hostility, she warms up to her after Rosie explains her situation, and the two become best friends. Carter teaches Rosie to act like the average American teenager, and Rosie shows Carter how to disarm those who scorn them, especially resident mean girls, Chelsea Barnes and Brooke Angels. Rosie soon becomes popular at their high school. In an attempt to trick Rosalinda into exposing her location, General Kane announces plans to forcibly marry her mother. Brooke discovers the truth about Rosie and threatens to expose her unless Rosie drops out of the vote for Homecoming Queen. Rosie reads of the pending nuptials in the magazine and tells Carter that she has decided to return home. Knowing Costa Luna is still too dangerous, Carter secretly devises a plan to pose as Rosalinda and use herself as bait to lure Kane into capture. Carter calls Mr. Elegante, Rosalinda's royal dressmaker and friend, for help with her plan. He tells Kane that Rosalinda will be attending the homecoming dance and plans to wear a Caribbean blue dress – he actually sends it to Carter and gives Rosie a pale pink one. In the meantime, Rosie agrees to stay for the dance. To help make the event special, a group of friends, including Rosie and Carter, wear masks to the dance, helping Carter disguise herself as Rosalinda. According to the plan, Kane and his agents mistake Carter for Rosalinda and lead her to Kane's helicopter. However, after winning the Homecoming Queen title despite Chelsea and Brooke's efforts, Rosie discovers and ruins the plan by exposing herself to Kane, insisting to Carter that it is not her fight. Luckily, agents of the Princess Protection Program, including Major Mason, have been waiting inside the helicopter and rescue both girls. The P.P.P. agents quickly apprehend Kane and his henchmen and turn them over to the international authorities. Rosie is crowned Queen Rosalinda of Costa Luna with Carter, Joe, Ed, Sofía, and Mr. Elegante in attendance. In the extended ending, one year later, Rosie and Carter, who both became P.P.P. agents, are getting ready for their new assignment as they board a plane.

Rosalinda: Since I've been here, I've learned many wonderful things. Most importantly, I've learned about friendship, loyalty, and trust. And that those are not things that are just given, but things we must earn. So, I want to thank Carter Mason for teaching me these things. And for being my friend. Carter Mason: What was I thinking? A guy like Donny would never go out with me. Rosalinda: Then he is not worthy of you. Carter Mason: Yeah, you can say that 'cause you're all high and royal. But I'm just a girl who sells bait. Rosalinda: No. You are so much more. You are a princess now. Carter Mason: Yeah. Trust me, I am not a princess. Rosalinda: Yes, you are. You just do not feel like one yet.