Juliette (Kristin Scott Thomas) moves in with her sister, Lea (Elsa Zylberstein) after getting released from a fifteen-year stint in prison for killing her son. Lea's husband does not trust Juliette, but over the course of the film they form a tight bond and become a family again.
Juliette's parole officer, who had been unhappy because his wife divorced him and took his daughter away, commits suicide. Juliette does a good job with the clerical work at the hospital and is offered a permanent job. Even though she will never be allowed to practice medicine again, Juliette is happy there. She uses the money to get her own apartment.
Lea accidentally finds a poem Juliette's son had written to her on the back of a medical form. Lea has a doctor friend interpret the results of the form and discovers that Juliette's son had terminal cancer. She confronts Juliette about it, and Juliette admits that she had diagnosed her son herself. She had kidnapped him from his father because she wanted to take care of him until the end, and gave him an overdose when she could no longer stand to see him in pain. She never revealed the cancer to the police because she had felt so guilty and unhappy that she had wanted to go to prison. Lea, who had been upset that Juliette never told anyone about the illness, comforts her sister -- indicating that the bond they had re-formed will stay in place.
Finally, we see Juliette walking with Michel, a colleague of Lea's, telling us that they will continue to explore their relationship.
Thanks Greg B!