Put in charge of his young son, Alain leaves Belgium for Antibes to live with his sister and her husband as a family. Alain's bond with Stephanie, a killer whale trainer, grows deeper after Stephanie suffers a horrible accident.
After suddenly finding himself face-to-face with a young son he hardly knows, Ali, penniless and friendless, takes refuge with his sister. Meanwhile, he meets a beautiful woman, Stephanie, during a night club brawl. Stephanie trains killer whales at Marineland. When a performance ends in tragedy, a call in the night again brings them together.
Ali (Matthias Schoenaerts) in his mid 20's, an unemployed father to a young son, Sam (Armand Verdure) arrives in Antibes, southern France to look for work. Having no money, he crashes with his sister Anna (Corinne Masiero) who already has her own share of problems with money and temporary employment.Ali gets a job as a bouncer in a night club but still keeps his passion burning for kick boxing. On a usual evening in the night club, Ali meets Stéphanie (Marion Cotillard) and escorts her safely to her home after she is injured in a brawl at the club. She works at a local marine tourist park where she suffers a tragic accident during a show and wakes up in the hospital to realize that her legs have been amputated.
Ali meets a guy at work who informs him about a kick boxing fixture he can make money from. Stéphanie, now in a wheelchair, is terminally depressed and gives Ali a call. Ali visits her and takes her to a beach where they swim.
Over a period of time, Ali and Stéphanie spend a lot of time together and get involved in casual sex every now and then, while Ali hooks up with other women as well, being honest about it with Stéphanie. Stéphanie starts to accompany Ali to the kick boxing matches and a symbiosis forms between both of them. Stéphanie starts to feel better about herself in Ali's company and gets artificial limbs. She starts to walk again and even manages Ali's bets for kick boxing. Ali, Stéphanie and some friends visit the same night club where Ali used to work. Ali goes to the dance floor and flirts with a girl as Stéphanie watches curiously. Ali goes away with the girl leaving a dejected Stéphanie with other friends.
Anna is fired from her job as the higher management comes to know of her taking home the expired food products. Anna blames Ali for this as Ali was involved in an odd job where he installed spy cameras in work areas at the direction of the management to spy on the activities of their employees. This results in a standoff between Ali and Anna's partner and Ali leaves. Sam stays with Anna while Ali goes to a training facility for kick boxers in a distant place and loses touch with Stéphanie.
Sam visits Ali at his facility for a day and both are shown playing on a frozen lake. A weak spot on the frozen lake cracks and Sam falls into the lake, loses consciousness and floats on. Ali takes a while to realize that Sam is nowhere to be seen. Once he spots Sam under the frozen lake, Ali releases a desperate volley of punches to break the surface and gets an unconscious Sam out. In the process, Ali fractures his hands.
Sam survives and in the hospital Ali breaks down while talking to Stéphanie on the phone and confesses his love for her after realizing that he had been cold and insensitive to her all this time. As the film closes, Ali is shown to have gone professional in kick-boxing as Sam and Stephanie stand by him in what looks like a post-fight victory ceremony.
