On a snowy winter evening in Dobbs Ferry, New York history teacher Paul Lohman (Steve Coogan) and his wife Claire (Laura Linney) along with Paul's older brother Stan (Richard Gere), a Congressman, and his wife Katelyn (Rebecca Hall) meet up for an organized dinner at an luxury restaurant that Stan has booked for just the four of them.Aside from the four patrons at the restaurant, Stan is accompanied by his personal aides: under pressure that he is the front runner in a race for Governor, as well as hemming an important bill through the House on the subject of mental health. It transpires during the course of the film - organized under chapter headings following the stages of the meal - that the four are there to discuss an incident in which their teenage children Michael (Charlie Plummer) and Rick (Seamus Davey-Fitzpatrick) verbally and physically harassed a homeless woman trying to sleep at an ATM kiosk leading to her death when Michael threw a lit match that set her sleeping bag on fire, killing her. A third boy, Beau (Miles J. Harvey), the adopted son of Stan and Barbara (Chloë Sevigny), Stan's ex-wife, left the scene before this occurred, but witnessed that this was an unprovoked attack.Over the course of the dinner, tensions run amok among the group inter-cut with flashbacks that view the dysfunctional family's past, and Stan's attempts to help Paul in his depression. The arguments grow more tense as they clash on whether the boys should take the blame or to simply cover up their wrongdoing.Paul's mental health, which has already become unstable after his wife's cancer diagnosis, finds it deteriorating further when he finds out that Michael uploaded a video of the woman's death online. Michael refuses to delete the video, causing a schism between him and his father. Paul also is shocked to find that Claire is colluding with Michael in a scheme to pay out thousands of dollars in hush money to anyone that finds out. After Stan and his wife offer to look after Michael while Claire is in the hospital, Paul becomes angry and accidentally hits him over the head with a saucepan.At the dinner, Stan makes it clear he wants to withdraw from the gubernatorial race and hold a press conference about the ATM incident, afterwards accompanying his son to the police. A bitter argument ensues between Stan on one side with turning his son over to the police, and Claire and Katelyn on the other who want to protect their children and their futures as well as their family's image and reputation, with Paul sitting quietly away from the table. Katelyn manages to persuade Stan to hold off on his plan to report Michael.Paul, broken and unstable, leaves the restaurant for Stan's house looking for Beau, believing that the solution to the problem is to kill Beau to silence him for good, and a violent confrontation ends with Paul threatening to hit Beau over the head with a rock.However, Paul is confronted by an enraged Stan, frantically looking for Beau, alongside Katelyn and Claire. While Katelyn tries to phone Beau, a call comes in to Stan's aide that the votes needed for the mental health bill are secure. The film suddenly ends on an abrupt note as Paul collapses and croaks out "Mental health for everyone!" as the others move beside him in the snow.