The film begins with Hubert Minel giving a black-and-white monologue explaining how he loves his mother but cannot stand being her son; he also reveals that when he was younger, things were better between them.
Hubert is a 16-year-old Québécois living in suburban Montreal with his single mother, Chantale, who divorced Hubert's father, Richard, when Hubert was much younger. Hubert barely sees his father, and this adds to the animosity between mother and son. One morning, as his mother drives him to school, Hubert starts an argument with her about her applying makeup while driving. The argument ends when Chantale stops the car and tells him to walk to school. At school Hubert claims to his teacher, Ms Cloutier, that his mother is dead. After the teacher finds out that it is a lie, she expresses this lie as "you killed your mother." This inspires Hubert to write an essay for school titled "I killed my mother."
Later in the film, Hubert's friend Antonin is revealed to be his boyfriend, but Hubert has not told his mother, and she finds out from Antonin's mother, who assumed that Chantale already knew. Chantale, to some extent, accepts her son's homosexuality; however, she appears hurt that he did not tell her. Hubert wants to live in his own apartment and is happy that his mother says it is a good idea, but the next day she has changed her mind and does not allow it, claiming that she thinks he is too young.
Their relationship continues to deteriorate, and Hubert goes to live with his teacher, pretending to be staying with his boyfriend. Hubert's father invites him over for a visit; however, once there, Richard and Chantale tell Hubert they've decided to send him to a boarding school in Coaticook. Hubert is deeply angered that his father makes the decision, since Hubert only sees his father at Christmas and Easter.
At the Catholic boarding school, Hubert meets Eric, with whom he has an affair. Eric invites Hubert to go to a nightclub with the other students, where they kiss and Hubert takes speed. He takes the Metro home, wakes his mother, and has an emotional conversation with her. The next morning, she takes Hubert to Antonin's mother's workplace to help drip the walls in paint. He and Antonin finish, and he lays down. Antonin proceeds to lay on top of him and kiss him, and they end up having sex. Hubert, later at home, trashes his mother's bedroom, but he calms down and cleans it up. The two fight and, in the morning, she sends Hubert back to the boarding school.
Back at school, Hubert is beaten by two fellow students. Hubert runs away with the help of Antonin, who has borrowed his mother's car. On the journey, Antonin tells Hubert that he is selfish and only cares about himself, but adds that he loves him. The school's principal calls Chantale to inform her of the developments, revealing the note Hubert left, saying he will be "In his kingdom". The principal also begins to lecture Chantale, which causes her to have an angry outburst at him, saying how he thinks he's better than her and how he has no right to judge a single mother. Chantale knows exactly where Hubert's "kingdom" is; the house he lived in as a child with both his parents.
Indeed, she finds Hubert and Antonin there. Chantale sits next to Hubert overlooking the beach. The film ends with a home movie clip of Hubert as a child playing with his mother.Xavier Dolan as Hubert Minel
Anne Dorval as Chantale Lemming, Hubert's mother
Suzanne Clément as Julie Cloutier, Hubert's teacher
François Arnaud as Antonin Rimbaud, Hubert's boyfriend
Niels Schneider as Éric, a boy at the boarding school
Patricia Tulasne as Hélène Rimbaud, Antonin's mother
Pierre Chagnon as Richard Minel, Hubert's father
Monique Spaziani as Denise, Chantale's friend
Benoît Gouin as Principal Nadeau, the boarding school principal
Xavier Dolan wrote the script when he was 16 years old. He said in an interview with Canadian newspaper Le Soleil that the film was partly autobiographical.
The film was at first financed by Dolan, but when need for more money arose, he asked both Téléfilm and the SODEC for subsidies. Both turned him down for different reasons. SODEC, who had loved the project but refused to finance it because it was submitted to a too commercial department, encouraged Dolan to submit it again in more appropriate "indie" department, which he did.
In December 2008, SODEC gave him a $400,000 subsidy. In all, the film cost around $800,000 CAD. Dolan said that the system to acquire funding is "[...] an obsolete financing mechanism that holds the creative assets of Quebec hostage."
The film received generally positive reviews from critics; review aggregator Rotten Tomatoes reports that 81% of professional critics gave the film a positive review, with an average rating of 7/10. Peter Howell from the Toronto Star said that "What makes it extraordinary is its depth of feeling, which Dolan's age makes all the more impressive: he was just 19 when he made this."
Peter Brunette from The Hollywood Reporter called it "Uneven but funny and audacious adolescent comedy from a talented beginner."
On 22 September 2009, Telefilm announced the film had been selected as Canada's submission for Best Foreign Language film at the 82nd Academy Awards. Despite this, it received no nominations at the 30th Genie Awards and received only the Claude Jutra Award for best directorial debut. Kevin Tierney, vice-chairman of cinema for the Academy of Canadian Cinema and Television, criticized the overlook, comparing it to "being sent to the kiddie table".