The stories of how legendary boxer Robert Duran and his celebrated trainer Ray Arcel changed each other's lives, and of the infamous rivalry between Duran and Sugar Ray Leonard. Arcel, the first boxing trainer to be elected into the Boxing Hall of Fame and trained over 2,000 fighters, is seen during his comeback after a retirement forced by the Mafia. Arcel agrees to train Duran for free, risking his one life, and beginning a journey that will change him forever.