This film follows the life of Roberto Duran, the legendary Panamanian fighter who made his professional debut when he was just 16 years-old, and his equally legendary trainer Ray Arcel who together changed each other's lives. In June 1980, he defeated Sugar Ray Leonard to capture the WBC welterweight title, but shocked the boxing world by returning to his corner in their November rematch, famously saying the words "no mas" (no more.)