In 2002, in Pittsburgh, Nigerian-born forensic pathologist Dr. Bennet Omalu performs an autopsy on Mike Webster, a former professional American football player. His investigation reveals severe brain damage linked to repeated head trauma sustained throughout Webster's career. By identifying a case of chronic traumatic encephalopathy in an NFL player, Omalu sparks a debate about the neurological consequences of the sport. Determined to bring his findings to light, he faces resistance from the powerful National Football League and begins a struggle to gain recognition of the risks faced by its players.