An oil worker from Stillwater, Oklahoma, named Bill Baker embarks on a journey to Marseille, France, to see his daughter, Allison, who is currently serving a nine-year prison sentence for a crime committed during her university years. Allison was convicted after the tragic death of her roommate and unfaithful lover, Lina.
During their initial meeting, Allison asks her father to deliver a note to her defense attorney, Mme. Leparq. Upon locating Leparq, Bill learns that the note reveals Allison has heard from a former professor about a man claiming to have information regarding Lina's murder. However, Leparq dismisses the leads as hearsay and refuses to reopen the case. In a moment of desperation, Bill lies to Allison, assuring her that Leparq intends to petition the judge for a new hearing.
While in Marseille, Bill encounters Virginie and her daughter Maya at his hotel. To gain further clarity on the note, he turns to Virginie for translation. Bill then seeks out the professor, who provides him with a contact number for someone claiming to know Lina's killer. Together with Virginie, Bill meets the informant, who reveals that the alleged killer's name is Akim.
As they dig deeper into social media, Virginie and her friends compile photographs of individuals from the circles of Allison and Lina. Bill takes these images to Allison, who identifies Akim among them. In his pursuit of justice, Bill confronts Akim at a housing project but faces violence from Akim’s associates, leading to the latter's escape. When Bill visits Allison again, he confesses to his deceit about Leparq's involvement and admits he found Akim without notifying the police. Furious and feeling betrayed, Allison demands that Bill never return to prison.
Four months pass, and Bill stays in Marseille, sharing an apartment with Virginie and working on a construction crew. One evening, while attending an Olympique de Marseille match, he spots Akim and follows him home. In a fit of rage, Bill confronts Akim, physically assaulting him before imprisoning him in the basement of the apartment where he lives with Virginie and Maya, insisting that Maya keep the secret.
To further investigate, Bill hires a private investigator to analyze a lock of Akim's hair against DNA from the crime scene. In a shocking twist, Akim claims that Allison hired him to kill Lina, offering him a gold necklace inscribed with the word "Stillwater" as payment. Struggling with doubt, Bill's faith in Allison begins to falter. The investigator’s curiosity grows, prompting him to disguise himself as a building inspector to question Virginie, who drops hints that raise suspicion even though she denies noticing anything unusual.
As the police come to search the basement, they question Maya, who lies to protect Bill, claiming she hasn't seen Akim. Once the officers leave, Virginie learns of Akim's captivity, leading her to confront Bill about putting Maya's safety at risk.
Eventually, Leparq informs Bill that DNA testing has exonerated Allison, yet his apathetic response confounds her. Following their return to Oklahoma, where they are greeted as heroes, Bill questions Allison about the Stillwater necklace he gave her before her departure to Marseille. In a moment of heart-wrenching honesty, Allison confesses that she did indeed hire Akim, though she maintains that she never intended for Lina to die. Standing by her side, Bill acknowledges the complexities of their family's legacy, remarking that Stillwater appears vastly different now.
