Anne is lawyer living in Denmark with her husband Peter and their twin daughters Frida and Franny, Peter's teenage son from his past marriage is Gustav, who lives in Sweden with his mother Rebecca. The family plans for Gustav to move in with Anne and Peter. Gustav arrives and Anne starts to form a relationship. Gustav begins to argue with Peter, pushing for the right to move out on his own despite being a minor and not being mature. One day, Anne returns home to find there has been a burglary. The incident is reported to the police, but afterwards Anne finds an item in Gustav's laundry that was in her bag, stolen during robbery. She realizes he was responsible for the robbery and confronts Gustav with the evidence. However, Anne promises to keep the matter a secret if Gustav does his part in the household. From then one Gustav cheerfully enjoys the family, for Example he reads the Danish version of Alice's Adventures in Wonderland aloud for the twin girls, which Anne herself also does. Time flies and one night, Gustav brings his girlfriend Amanda home he introduces her to Anne. Anne hears the couple having sex and is annoyed by it. Peter and Anne entertain guests on their balcony, but Anne leaves the group to lure Gustav to a bar. There, she kisses him. After that at night, she enters his bedroom and seduces him by initiating sex. The two begin a love relationship in a secret; Gustav interviews Anne with a tape recorder, asking her various questions including about her first sexual relationship. Anne says it was with someone she shouldn't had it with, Anne refuses to talk about who it was. The family celebrates the twins birthday. When Anne and Gustav step away, Gustav kisses her, Anne tries to stop him by saying not here. Anne's sister Lina, witnesses the encounter on front of her and, gets upset so she leaves the party. Gustav and Peter leave to spend time at their cabin in the woods. After their return Peter tells Anne that Gustav wants to go to a boarding school, and had told him about the affair that he had with Anne. After the conversation Anne denies the claim, saying Gustav hates her for ending Peter and Rebecca's marriage and why would she have an affair with his son. She also tells Peter that Gustav was responsible for the burglary. Anne, Peter, and Gustav then sit down together, where Anne continues to deny about the affair, Gustav gets really angry that he wasn't lying about it. Gustav leaves for a boarding school. Much later Gustav visits the office of Anne and threatens her that if she doesn't tell Peter the truth he will report about the illegal affair of a child having sex with an adult, but she replies that nobody will ever believe him. He bangs on her house at night asking for his father but he is rejected by Anne who tells him that he is no longer apart of the family, he begins to kiss her on the neck and lips but she managers to push him away, he starts crying on the ground. At a party for Anne, Peter is called with the message that Gustav is missing from his school. Peter is called to Stockholm by the police. It turns out that a hunter had found Gustav's body near the cabin, where he froze to death. Anne begins to cry in the bathroom because it was her fault, she then sees an illusion of Gustav behind her. When Anne tells Peter that Gustav's death is not his fault, Peter violently shuts her up. The family drives to Gustav's funeral.