Steelers center Mike Webster is found dead in his pickup truck, after years of self-mutilation and homelessness. Before his death, Justin Strzelczyk, a former fellow football player, confides in Webster that he is starting to lose his memory, is saying odd things to his children, and nearly threw his wife against the wall. A disoriented Webster brushes Strzelczyk’s worries off, and deliriously tells him that the most important thing “is to finish the game,” reciting what he said during his Hall of Fame speech.
Dr. Bennet Omalu (Will Smith), a forensic pathologist with the Allegheny County, Pennsylvania coroner’s office, handles Webster’s autopsy. He wonders how an otherwise healthy man could have degenerated so quickly, and makes it a point to figure out why he died of a heart attack at only fifty years of age. Dr. Omalu closely examines microscope slides of Webster’s brain and sees evidence of severe neurotrauma, concluding that Webster died as a result of the long-term effects of repeated blows to the head, a disorder he terms chronic traumatic encephalopathy (CTE). With the help of former Steelers team doctor Julian Bailes, fellow neurologist Dr. Steven DeKosky and county coroner Dr. Cyril Wecht, Dr. Omalu publishes his findings in Neurosurgery, which are dismissed by the NFL.
Over several years, Dr. Omalu discovers that three additional deceased NFL players, Justin Strzelczyk (2004), Terry Long (2005), and Andre Waters (2006), exhibited symptoms very similar to Webster’s. He persuades newly appointed NFL commissioner Roger Goodell to allow him to present his findings before a player safety committee. However, the NFL does not take him seriously, and he is barred from the committee meeting, forcing the former NFL employee Bailes to give the presentation in place of Dr. Omalu. However, the meeting is a set up, where the NFL claims that the players’ head trauma is unrelated to football, but rather, due to past injuries. As he leaves the meeting, former NFL Players Association executive Dave Duerson angrily confronts Dr. Omalu and tells him to “go back to Africa.”
Dr. Omalu is subjected to considerable pressure to back down from his efforts, as football is a widely beloved sport in Pittsburgh, having provided jobs and allowed men to go to college. Wecht is subjected to a politically motivated prosecution on corruption charges, and Dr. Omalu is forced to leave Pittsburgh soon after, lest he be deported, or sent to prison on petty charges as punishment for tarnishing the NFL’s image. Before leaving, he urges the NFL to tell the truth. Dr. Omalu’s wife, Prema, suffers a miscarriage after being followed in her car. The Omalus are forced to leave their dream home outside Pittsburgh, relocating to Lodi, California where he takes a job with the San Joaquin County coroner’s office.
Three years later, Dr. Omalu is vindicated when Duerson commits suicide due to an increasing inability to cope with worsening cognitive function. In his suicide note, Duerson acknowledges that Dr. Omalu was right, and offers his brain for future research. Dr. Omalu is invited to address an NFLPA conference on concussions and CTE. He informs them that he once wished he had never known Mike Webster, but by knowing him, he has the responsibility to inform NFL players of the true risks that they take by playing. He says that he holds no resentment for the NFL and tells them to forgive themselves and be at peace. Amid growing scrutiny from Congress, the NFL is forced to take the concussion issue more seriously, and in 2011, NFL players sue the league for not properly informing them of the risk of CTE. Dr. Omalu is offered the job of Chief Medical Examiner for the District of Columbia, but the closing credits show Omalu turning the offer down to remain with his family in Lodi, becoming naturalized as a U.S. citizen in February 2015. A final montage includes reports of Junior Seau’s suicide in 2012 and subsequent lawsuits brought against the NFL by thousands of former players.