Bryan Mills (Liam Neeson) is a retired CIA operative, called a "preventer", from their elite Special Activities Division. He has retired to spend more time with his 17-year-old daughter Kim (Maggie Grace), who now lives with his ex-wife Lenore (Famke Janssen) and her new wealthy husband Stuart (Xander Berkeley). When pop diva Sheerah (Holly Valance) comes to town, Mills is hired for security. After the show, Sheerah is attacked, but Bryan disables the assailant and gets her safely out of danger. Thankful, Sheerah expresses some interest in Mills' daughter after learning that Kim wants to be a singer herself. Sheerah passes along her contact information.
The next day, Mills discovers that Kim wants to take a holiday trip to Paris, with her friend Amanda (Katie Cassidy). Despite his initial concerns about the trip, Mills allows her to go, later discovering that their actual plan is to travel around Europe following the band U2. Arriving at the Paris airport, Kim and Amanda meet a Frenchman named Peter (Nicolas Giraud), who learns their address and reports it to an unseen associate.
In the house, Kim receives a phone call from her father, which she answers in the bathroom. From the bathroom window, she sees men entering the main room and abducting Amanda. Mills is able to gain critical information about the kidnappers in the final moments after Kim is kidnapped by telling her to shout out everything about them that she notices. Briefly, Mills talks to one of the kidnappers, warning him that unless Kim is released, he will pursue him and kill him, to which the kidnapper replies "good luck" before smashing her phone.
Exploiting government contacts and the business connections of his ex-wife’s husband, Mills travels to Paris to find Kim, informed that the kidnappers are (Albanian mafia) lead by a man named Marko, and that he has only 96 hours to recover his daughter before she will "disappear forever". Mills uses digital photos from the memory card of the smashed remains of Kim's phone to locate Peter, who is killed by an ice cream van while trying to escape. Mills manages to save one of the kidnapped girls from the Albanians, and she discloses to him the address of the house where the kidnappers are holding other girls. Mills finds the house and several other abducted women - including Amanda, who is dead from a forced overdose. Later, by torturing Marko, Mills learns that Kim was sold to a man named Patrice Saint-Clair, who showed interest in making a profit from selling her. After wreaking havoc in the streets of Paris, Mills is hunted by the French authorities, including his old ally Jean-Claude (Olivier Rabourdin), who wants him to return to the United States. Undeterred, Mills forces Jean-Claude to give him Saint-Clair's location by shooting Jean-Claude's wife in the arm and revealing he knows Jean-Claude received bribes for overlooking the trafficking.
By impersonating Jean-Claude, Mills gains entry to the building where new girls are being sold, and secures entry to one of the buyers’ viewing booths. He sees his daughter as she is displayed on the auction block. However, he is captured before he can engineer an escape for himself and Kim. Mills manages to escape and find Saint-Clair, whom he kills after learning that his daughter is being taken by Qatari clients. Mills manages to follow the car Kim is being taken in, and sees her being transported away on a yacht. He jumps on to the ship from a bridge and kills everyone in his way, finally freeing his daughter. Back in the U.S., Kim is reunited with her mother, and Mills finally introduces her to Sheerah, having arranged an audition with her vocal coach.