Will Smith stars as Dr. Bennet Omalu, a well-educated, Nigerian-born forensic pathologist working in Pittsburgh, who, in 2002, discovers a type of degenerative brain injury that seemingly has resulted from those who play football, America's most popular and lucrative sport. After diagnosing the deceased brains of a couple of deeply troubled professional players who exhibited progressively erratic behavior before ending their lives prematurely after many years of taking blows to the head on the field, Dr. Omalu publishes his startling findings in a research paper, calling the disease CTE (chronic traumatic encephalopathy), and immediately begins to draw interest from many parties, some who want to help, and others who want to discredit or silence him from potentially taking down an industry worth billions of dollars.