Twelve-year-old Justine's parents are recently divorced and she and her little sister, Bea, go back and forth between their parents' homes in Montreal. Because her mother (whose anxiety manifests itself as the need to control) believes that their father and beloved half-sister are a bad influence on Justine and Bea, she enlists Justine's aid in collecting evidence that would lead to sole custody being granted to her. Justine goes along with this plan, and buys into her mother's view of her father at first, but when she crafts an outright lie for her mother's court case, she starts to question her mother's--and her own--behaviour. When called upon to testify in court in front of a judge who actually cares about Justine and Bea, Justine is able to summon the courage to tell the truth, no matter what the consequences.