After budget cuts cost him his job as a high school teacher, Lucas takes a job as a preschool teacher in the close-knit Danish community where he grew up. He is divorced and struggles to maintain a relationship with his teenage son, Marcus. Marcus lives with Lucas’ ex-wife, but he eventually decides to move in with Lucas. Nadja, a Russian emigrant and another teacher at the preschool, makes advances on Lucas and eventually becomes his girlfriend.
One of Lucas’ students is a five-year-old girl named Klara, the daughter of his best friend, Theo. She has an innocent crush on Lucas, who treats her kindly, whereas her parents constantly argue; he also lets her walk his dog, Fanny. One day, Klara puts a heart-shaped ornament into his coat pocket, then gives him a kiss on the lips. After Lucas admonishes her, Klara’s feelings are hurt. Drawing on a memory of a pornographic photo her older teenage brother and his friend showed her, she makes comments describing an erect penis; this leads Grethe, the preschool director, to believe Lucas exposed himself to Klara. Grethe brings in a psychologist who asks Klara leading questions about what occurred; Klara gives unclear responses about Lucas, alternately denying and confirming the abuse.
Grethe doesn’t believe that a child would lie about such a serious matter. She informs the other parents that Klara was likely abused; she also advises them to look for signs of sexual abuse in their own children. The parents ask leading questions of their children, who also say they were abused, thereby destroying any public doubt about Klara’s story. Lucas is fired, and the community quickly shuns him, labeling him as a paedophile.
Lucas tries to get some answers out of Grethe, but she is still convinced that the children are telling the truth. Johan, one of Lucas’ drinking buddies, leads Lucas away and orders him to go home.
Lucas shows up to Theo’s house and suggests that the two of them discuss the issue with Grethe before things get worse. However, Theo insists that his daughter has never once lied, and he says he isn’t sure whom to believe. Theo’s wife, Agnes, on the other hand, is certain that Lucas is guilty; she becomes enraged and throws him out, refusing to listen to his protests. As Lucas is leaving, Theo grabs him, pins him against the wall, and threatens to kill him if the accusations turn out to be true. After Lucas has left, Klara tries to tell her mother that he didn’t do anything, but Agnes merely believes that Klara is in denial.
Lucas’ friendship with Theo is subsequently destroyed. His relationship with Nadja is likewise ruined when she expresses uncertainty at his innocence, causing him to angrily throw her out of the house. Marcus, who arrives to move in with Lucas, becomes ostracised by association, and he is told by a grocery employee that neither he nor his father are welcome to shop there anymore. Lucas survives only with the financial support of his close friend Bruun—whose father is extremely wealthy—and of a few friends who still believe him.
Lucas is arrested on suspicion of sexual assault. However, the children’s accounts all involve Lucas abusing them in his basement, which supports Lucas’ innocence as his house has no basement. After a hearing, Lucas is released without charge, and he celebrates with Marcus and Bruun.
Despite the ruling, the community still believes Lucas is guilty, and the ostracism turns into violence. Lucas’ dog is killed, and a large stone is thrown through his kitchen window. Marcus decides to take matters into his own hands and visits Theo, who lets him enter his house as Marcus is friends with Klara’s teenage brother. In front of the other half of Lucas’ and Theo’s group of friends, who have sided with Theo, Marcus accuses Klara of lying and spits at her, and is promptly attacked. He is only spared serious injury by Theo, who intervenes and tells Marcus to leave. Deciding that the situation is too dangerous, Lucas sends Marcus away to live with his mother. Without his son as an in-between, Lucas is forced to go grocery shopping himself, and when a butcher at the grocery store viciously assaults him, Lucas retaliates by breaking his nose.
On Christmas Eve, Lucas reaches his breaking point; he angrily confronts, then beats Theo in front of everyone during a church service, telling him and the rest of the town to leave him alone. That night, Klara, mistaking her father for Lucas, apologizes to him as she drifts off to sleep. She insists that she didn’t want things to turn out this way and that Lucas did nothing wrong. Realizing Lucas’ innocence, Theo later visits him with food and alcohol as a peace offering.
A year later, tensions in the community have simmered down, and everyone seems to have welcomed Lucas back in. Lucas and Nadja rekindle their relationship, and Marcus is accepted into the local hunting society as an adult. On a hunting expedition to commemorate the event, someone apparently shoots at Lucas with a rifle and barely misses. Blinded by the setting sun, Lucas is unable to identify his attacker. A moment later the unknown shooter flees in to the forest.