Scott approaches the courthouse and walks through a throng of reporters. They are all asking him about his dead son. He is ambushed in the lobby by a armed man who shoots him with a paintball gun and screams the word" Murderer".
We see Scott in his element as a pediatric brain surgeon. He is interrupted by his wife's urgent call from their son, Devin's school. Devin has threatened several students who his mom believes to be his bullies.
The school wants to assess his behavior for mental health concerns and imply he is mentally ill. Refusing to listen, Lynn pulls him out of school.
She immediately works to get him into a prestigious private school. Devin is petulant to both of his parents on the ride home. His dad wants them to address the threats but Devin is unrepentant.
They are interrupted by the neighbor's barking dog. Devin storms away.
Scott watches home videos that portray Devin to be a troubled child. We see example after example of Devin hurting his mom, animals and other children. We also see their other child who is also concerned about Devin.
Scott and his wife have a difficult conversation about Devin's lack of empathy. She defends him with other possible perspectives. She refuses to believe that he is dangerous and dismisses her husband. They argue about Devin.
Devin listens to the fight while drawing in a handwritten notebook. The notebook contains graphic and violent imagery.
The judge advises the information given during this preliminary trial will determine if Scott will stand trial for murder.
In another flashback, we see Scott attempt a conversation with Devin. Devin is generally nasty and threatening until they are interrupted again by the neighbor's dog. Devin suggests someone kills the dog.
Scott snaps at an intern during surgery and reveals to his co-worker that he is concerned about his son being violent.
Scott sees his neighbor posting missing dog posters. He confronts his son about the dog and his son speculates that someone poisoned the dog.
Scott raids his son's room and finds his manifesto. He shows his wife. There are graphic pictures of the girl Sabrina that Devin threatened at school. In the manifesto, Devin writes that he will wipe her off the face of the earth.
Lynn finally believes her son is a sociopath. She cries into her husband's arms, but they fail to find a solution.
Scott again confides in his friend Mitch that he believes Devin will hurt someone soon.
He believes that a 72 hold would not be enough and that going to the police will be fruitless.
He confides that he would feel relieved if his son died.
Mitch is now a witness for the prosecution. He admits that Scott knew Devin could harm someone. The prosecutor questions if he had planned to murder his son at Deep Gorge.
In a flashback, we see Scott researching articles about the dangers of Deep Gorge. He reads how many hikers fall off the cliffs.
Scott apologizes for accusing Devin of hurting the dog and invites him on a hiking trip. He bribes him with an offer of money.
He packs to go and his wife is relieved and appreciative that he didn't give up on his son.
In the woods, the father and son hike, and Devin complains. He explains how this place meant a lot to Devin as a child. They camp out for the night and Scott attempts to start a fire. Devin walks up behind him with an axe and it appears he is going to stab his father.
He instead offers it to his father to kindle the fire. Scott has multiple opportunities to harm Devin but he doesn't take any. Devin confronts his father about the attempt on his life and tells him he doesn't want to feel this way anymore.
Devin asks for the money again and in a rare moment of emotion reveals that he doesn't want to hurt anyone. He says that he made up all the threats.
He wants to take a 2-month long hike with his friend Jax and clear his mind of his violent thoughts. He convinces his dad that he really wants help and he will seek therapy when he returns.
His dad believes him and when they go home, he appears to be a new child. He offers to help his dad with the luggage and he hugs his parents good night. They are astounded.
The prosecutor calls Jax (Devin's friend who is going on the hike) to the stand. They use him to prove that Scott gave them $10000 and did not actually believe in his son's change of mind. It is determined that Devin used the money his dad gave him to buy AK-47s.
The next day, Scott brags to his friend Mitch that Devin has changed his ways. He confesses he gave his son a large sum to help his son. While they eat lunch, a breaking news report shows a barricaded gunman at Devin's school.
He arrives on the scene and the police take him aside immediately upon identifying Scott. We discover that Devin is the gunman. Bodies are being carried away on stretchers, while people are glaring at Scott and helicopters circle the school.
Devin refuses to talk to anyone but his father. Scott gets on the phone with him and Devin tells him that he should've killed him on the hike. He then blames his father for everything before shooting and killing himself.
We learn that Scott is not being tried for his son's murder, but as an accessory to the mass shooting. The state believes his inability to act and report the threats made him directly responsible for the deaths at Devin's school.
Scott is found not guilty. His surviving son refuses to hug him in celebration. Lynn, his wife, asks him did he actually take Devin to the woods to kill him and Scott begrudgingly admits it is true.
She tells him she wishes he had killed Devon when he had the chance.