Omalu is the real-life doctor who, while working as a forensic pathologist in Pittsburgh, discovered a new and terrifying brain disorder that he named Chronic Traumatic Encephalopathy, or CTE. He discovered it performing an autopsy on a retired Pittsburgh Steeler named Mike Webster (movingly portrayed here by David Morse). Webster left the game as a hero and began losing his mind well before his death at fifty; scenes shortly before his death show him living in his pickup truck, huffing turpentine. A fellow player, himself to suffer a similar fate in the movie, tries to help him out. Neither man understands what’s happening to them. Omalu figures it out: the persistent head injuries sustained in football play shake up the brain—as the character explains, unlike some other mammals, humans don’t have built-in shock absorbers for their grey matter—and release a protein that builds up and causes hallucinations, memory loss, and much more trauma.