In less than a month, the NFL season will officially begin when the Super Bowl Champion Baltimore Ravens travel to Denver to face the Broncos on Thursday Night Football. America’s indisputable national pastime will be back.

But it’s not just players and coaches that will be returning to the field. The start of the season marks a return to the spotlight for an issue that continues to be a public relations nightmare for the league: brain injuries.

This fall, FRONTLINE will air a special two-part investigation examining whether — as thousands of former players allege — the NFL has covered up the risks of football on the brain. Watch the trailer below.

Drawing on the forthcoming book League of Denial (Crown Archetype, October 2013) by Steve Fainaru and Mark Fainaru-Wada of ESPN, the film will explore what the league knew and when, what the truth is about football’s effect on the brain, and what can be done.

The film, League of Denial: The NFL’s Concussion Crisis, will air on FRONTLINE on October 8 & 15. Check your local listings here.