Christian Longo (James Franco), an Oregon man whose wife and three children have been discovered murdered, is arrested by police in Mexico, where he had been identifying himself as a reporter for the New York Times named Michael Finkel.In New York City, Michael Finkel (Jonah Hill) is an ambitious and successful reporter. He is confronted by his editors about a story he has written which featured on the cover of the New York Times Magazine. They accuse him of using a composite character as the focus of his story, a violation of basic reporting principles. Finkel briefly attempts to defend his actions, but he is unsuccessful and is fired. He returns home to his wife Jill (Felicity Jones), and struggles to find work as a journalist due to his public firing from the Times.Finkel is contacted by a reporter for The Oregonian,seeking his opinion on Christian Longo's assumption of his identity. Finkel, who was unaware of Longo's case, is intrigued, and arranges to meet Longo in prison. During their first conversation, Longo claims he has followed Finkel's entire career and always admired his writing. Longo agrees to tell Finkel his side of the crimes he is accused of, in exchange for writing lessons and Finkel's promise not to share their conversations until after the conclusion of the murder trial.Finkel becomes increasingly absorbed with Longo, who is likeable but evasive about his guilt. Convinced the story will be redemptive, Finkel visits Longo in prison and corresponds with him for several months. Longo sends Finkel numerous letters as well as an 80-page notebook entitled "Wrong Turns" which contains what Longo describes as a list of every mistake he has made in his life. Finkel begins to recognize similarities between Longo and himself, their handwriting and drawing, and Longo's letters and Finkel's personal journals. As the trial approaches, Finkel grows increasingly doubtful Longo is guilty of the murders, and Longo informs Finkel he intends changing his plea to not guilty.In court, Longo pleads not guilty to two of the murders, but pleads guilty to the murder of his wife and one of his daughters. Finkel confronts Longo, who claims he cannot share everything he knows, because he has to protect certain individuals who he refuses to name. Greg Ganley (Robert John Burke), the detective who tracked Longo down and arrested him, approaches Finkel and claims Longo is an extremely dangerous and manipulative man. He tries to convince Finkel to turn over as evidence all his correspondence with Longo. Finkel refuses and Ganley does not press him for an explanation.At the trial, Longo takes the stand and describes his version of the events in detail. He claims he had, after an argument with his wife about their financial situation, come home to discover two of his children missing, one of his daughters unconscious, and his wife sobbing, saying she put the children "in the water". Longo says he strangled his wife to death in a blind rage. He says he thought his other daughter was dead at first, but then realized she was still breathing and strangled her as well because she was all but dead. Finkel's wife, Jill, watches Longo's testimony.As the jury deliberates, Jill visits Longo in jail and tells him he is a narcissistic murderer who will never escape who he is.Longo is found guilty of all four charges and sentenced to death. After he is sentenced, he winks at Finkel, who, to his shock and rage, realizes Longo has been lying throughout their conversations, using him in order to make his testimony more believable. A short time later, Finkel meets Longo on death row. Longo tries to convince Finkel he discovered his wife strangling their daughter and then blacked out, so he has no memory of the murders. Finkel angrily tells Longo he will not believe any more of his lies and will warn the judge, when Longo appeals against his sentence, of Longo's manipulative nature. Longo retorts by pointing out the success Finkel has had with his book about their encounters, leaving the reporter shaken.Finkel reads a section of his book, entitled True Story, at a promotional event in a bookstore. Taking questions from the audience, he imagines Longo standing in the back of the room. Longo says if he has lost his freedom, Finkel must have lost something as well. Finkel is unable to respond.Title cards reveal Longo admitted, a year later, to killing his entire family. Finkel never wrote for the "New York Times" again, but Longo has contributed articles to a number of publications from death row, including the "New York Times." The final title card says Finkel and Longo still speak on the first Sunday of every month.