The movie opens with scenes of a small town in Texas. Grace (Selena Gomez) is a waitress in a diner. She serves some of her former high school classmates and tries to make small talk with them; however, they are snotty to her. Owen (Cory Monteith) comes in and kisses Emma (Katie Cassidy) who also works there. They are counting down the two days left until they go on vacation to Paris.
Cut to their high school graduation. In the middle of the valedictorian speech, Grace’s stepsister named Meg (Leighton Meester) makes a noise while coming in, interrupting the ceremony and speech. Grace runs out to hug Emma and see her family. She’s upset that Meg is there as they pose for pictures. Emma tells Grace’s mother Pam (Andie MacDowell) not to worry, she’ll take care of her on vacation.
While eating dinner, Grace’s stepfather gives her a suitcase as a gift for her vacation. They tell them that Meg is going to Paris with Grace and Emma and he upgraded them to first class. Meg, who doesn’t think highly of Grace and Emma, is very upset as she doesn’t like Emma and doesn’t want to be Grace’s babysitter. Her father wants her to go because he feels as though since her mother died she hasn’t lived her life.
Meanwhile, Owen is upset that Emma is going to Paris without him. He spontaneously proposes to her as she gets out of the car. At first she’s excited, but she knows he’s only asking her because he’s jealous. They argue, and she leaves his car.
Back at Grace’s house, she and her mother talk about her concerns about the trip. She doesn’t want Grace to go alone with Emma, and that’s why they decided to have Meg go as well. Grace tells her that she wants to find a life just like her mother did with Robert. She decides to take Meg with them.
As they travel on the tour bus, in Paris Meg is complaining they won’t have time to see everything as they just pass by all the sights quickly. They finally get a good view of the city but can’t stay because they have to catch up with the group. As they climb the stairs they bump into a cute, nice, Australian.
As they are eating dinner, the plates are taken away before they can even eat their food. Their hotel room is not what it looks like in the brochure it’s very crummy! Their only view is of a man bathing in another room!
The next day the bus takes them to the Eiffel Tower. Meg buys a charm for her bracelet which belonged to her mother (Paris was her favorite place too). While at the top of the tower, they see the Australian guy again who is looking at Meg. He goes to talk to her, and introduces himself as Riley while Grace notices that their tour is leaving without them. They have to leave him as they run to catch up with their tour but Emma can’t run fast with or without her heels. They miss their bus and the girls are arguing on the sidewalk. Grace is very upset as she apologizes and becomes angry at herself.
They run through the rain to try and find their hotel and are suddenly photographed by paparazzi. They run inside a building, which is a beautiful four star hotel. When they get inside there’s a woman at the counter who looks exactly like Grace Cordelia Winthrop Scott. She’s being rude to the employees.
Cordelia goes into the bathroom where Meg and Emma are staring at her as she talks on the phone. Cordelia leaves and Grace comes out, wondering why the other girl, Cordelia, was being snotty on the phone. They play with Grace’s hair and tell her that she looks just like Cordelia and to just add a British accent. She fools around with it as they leave the bathroom and the concierge at the hotel thinks she is Cordelia, so they offer her a 26 lb lobster.
They go to Cordelia’s room, which is beautiful. Meg doesn’t want to stay there, but Grace and Emma get under the covers and tell Meg to go to bed and they’ll “bond.” Meg agrees to stay until it stops raining and they go to sleep. The next morning they are woken up by the phone and Grace keeps saying “wee wee” on the phone. She says she thinks their car is there. They go downstairs where all Cordelia’s luggage is being carried out. The concierge gives her a package, and they thank him and try to leave as they are photographed by paparazzi. The car takes them to the airport.
Emma rips open the package which has her itinerary on it they are going to Monte Carlo. Emma and Grace want to go and continue their adventure; however Meg is against it. They get on the private jet and Cordelia is on the cover of a magazine on the plane. She’s an heiress who has apparently gotten into some trouble in the past.
The girls arrive in Monte Carlo and are greeted by a man and his son Theo (who thinks she’s a brat) on behalf of the children’s benefit they are there to support. Theo seems to know something is up with Grace. He tells them that he will escort them to the ball and leads them inside. When they get to their room, Meg and Grace don’t want to stay but Emma tries to convince them that they will be fine. Emma tells them the new plan is to have fun in this adventure.
They open up giant makeup, dress, and shoe cases as they get ready for the ball. They also discover beautiful jewelry. The girls get off the elevator all glammed up and walk down the stairs to the annoyance of Theo who tells them that they’re late. As they go inside they are surrounded by paparazzi. Grace asks Theo why everyone is staring at her and he says it’s because of the necklace she’s wearing which is going to be auctioned that Friday. He shows her a poster for the fundraiser which is an education initiative. He tells her that he’s admiring her boots (she forgot to take them off). He starts introducing her around and a cute prince asks Emma to dance. While Theo goes to see his parents Meg gives Grace a quick summary of Cordelia’s life and things she should know.
Cordelia’s Aunt Alicia comes by and notices there’s something different about her, and Grace, pretending to be Cordelia, tells her to tell her mother she’s fine and runs off with the girls.
Meanwhile, back in Texas Owen is sitting at the diner. He calls Emma’s phone but the man at their hotel answers and says she’s not available. Owen, worried, flies to Paris but the concierge at the hotel tells him that she’s gone.
The next day the girls are being waited on at the beach. Emma and Meg still aren’t getting along and start a big argument. Emma accidentally brings up the fact that Meg’s mother died, upsetting her and causing her to leave.
Meg is wandering around and suddenly sees Riley, the Australian from Paris. She tells him that they missed the bus, and while this is happening, Theo picks up Grace on the street, noting that there’s something different about her (no accent). She gets in the car and gives him the “Cordelia” attitude. They pass by Meg and Riley on a motorcycle but don’t notice one another.
Theo drops Grace off at a function where her aunt is. She goes to change and realizes she has to play polo. She makes mistakes as she doesn’t know how to play the game. Aunt Alicia notices something strange is going on and during the game she calls Cordelia’s phone and she picks up. She approaches Grace and asks her what her childhood horse’s name was, which of course she can’t answer. She thinks that Cordelia hired a lookalike and threatens to call security, but Grace asks her not to so that nothing will get in the way of the charity event. Later, as she grooms the horse, Theo approaches her. She tries to teach him how to whistle with his fingers in his mouth which he can’t do. He tells her she’s different than he expected her to be and that she makes him feel different. Theo tells her that all the charity work is his father’s, and he’s only faking his way through life. They then go off to watch fireworks together and continue talking about their “magical” evening.
Meg continues to enjoy her time with Riley, going swimming and talking. They talk about a rugby accident that almost paralyzed him and she talks about her mother and her death. He tells her to scream to get her anger over the situation out, but she says she can’t.
Emma is back at the hotel and sees a huge bouquet of flowers there. It’s for her from the prince she danced with at the ball. She gets ready for a date with the prince and puts on the necklace. In the car with the prince she sees Meg on the motorcycle with Riley. They talk and apologize to one another for what they said earlier and go their separate ways with their men. Meg makes Emma take off the necklace first through and puts it in Riley’s bag on the motorcycle before taking off.
Emma and the prince go to a party on a boat and Emma is loving her new first class experience at first, until she notices that she doesn’t quite fit in with the rest of the dinner guests as they are not very nice to the waiters. Emma, being a waitress herself, picks up some of the plates and leaves to watch the fireworks by herself, happy being who she is. Meg goes dancing with Riley and they also stop to see the fireworks. Meg seems to be having the time of her life.
Theo takes Grace back to the hotel and she tries to tell him the truth, but decides to do it the next day. She goes to her room and sees Emma in bed watching a movie with Grace Kelly. She tells Grace that she thought she and Owen would live in a fancy house one day together, but now she realizes she doesn’t care about the house, all she wants is Owen and she hopes she didn’t blow it. Grace tells Emma that she finally met a guy that likes her for her, and it’s not even really her. She’s worried that Theo will hate her when he finds out the truth.
They notice that Meg isn’t there she’s outside with Riley running around having fun together. They don’t get back until the morning. Riley’s impressed with her hotel and tells her he’s leaving at noon to catch a train to Italy and he wants her to go with him. She kisses him goodbye and says she can’t. She goes back to the room and realizes that she left the necklace (worth millions) in Riley’s backpack. They have 20 minutes to get to the train station to get it back.
Owen, who has been sleeping outside, is woken up. He sees the three girls on the cover of a newspaper and catches a train to Monte Carlo.
Just then they look down off the balcony and see the real Cordelia get out of the limo and goes to check into the hotel. Once again, she’s very rude to the concierge. Upstairs, the girls are frantically trying to clean the room and get out. Theo arrives at the hotel and seeing Cordelia kisses her. Not knowing who he is, she slaps him. When Cordelia gets inside the room, she’s not happy because she doesn’t think it’s big enough. She walks onto the balcony, not seeing the girls who are standing on the side of the balcony trying to hide. They can’t get back inside however because the doors are locked and have to climb along the entire building. They get to the train station right at 12 and see it leave. They sit, depressed, and Grace says she has to fix this situation somehow. They leave the station, not noticing Owen who is also there.
Meanwhile, Cordelia is complaining on the phone about how she never gets to do what she wants. She notices a half eaten apple and the newspaper with the girls’ picture on it. She opens the jewelry box and sees the necklace is missing, screaming in horror.
Back at the hotel we see Riley who decided not to leave after all. As he inquires at the front desk, the concierge talks to Cordelia on the phone who wants the police, but he just keeps saying security. The three girls arrive back at the hotel and the concierge asks them about the robbery. Just then Theo shows up and asks Grace what’s going on is she playing games? They say they’ll be right back and Grace kisses him. They have five minutes before the auction.
The girls see Riley and get the necklace back while Meg kisses him and tells him not to leave. The police show up at the hotel to the horror of the concierge, who is talking to Owen. Cordelia opens the door to her room and sees Grace, Emma, and Meg standing there ready to explain what’s going on. To stop her from calling the police again, the girls hold Cordelia down and tell the police the scream they heard (which came from Cordelia) was excitement in finding the necklace and there’s no problem. Grace comes out and asks Theo to put the necklace on her. In the other room of the suite, Emma has tied up Cordelia and stuck an apple in her mouth, saying they’ll let her go when he auction is over.
Downstairs, Owen sees Grace and Meg walk by and he and Riley are confused. Meg tells Owen to stay there but he doesn’t listen and goes to find Emma upstairs. They’re both happy to see one another and talk in the hall.
Meg and Grace arrive at the charity event and the necklace is up for auction. In the middle of the bidding, Grace tells everyone the necklace isn’t hers. Cordelia escapes from the hotel suite and gets to the event exposing the truth at that moment. Grace admits she’s not Cordelia with the girls sticking up for her, however Theo is very upset and leaves. Grace says how much the kids need the money, and Aunt Alicia bids 6 million Euros for the necklace. Cordelia still tries to get them arrested by nothing happens.
Later, the girls are outside the hotel. Meg tells Grace she’s decided to stay in Europe with Riley until August. Grace, Emma, and Owen get on the plane and Grace tells her mother over the phone they had an amazing time, although she’s very upset about Theo.
As the summer progresses we see Meg and Riley climb to the ruins and scream loudly together. Back at home in Texas, Owen is working on the house he and Emma now share. Grace is volunteering with kids in France and goes on an errand to the post office. Theo shows up where Grace is working and goes after her, whistling like she taught him. They reintroduce themselves to one another.
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