The Clay family scrambles to secure Cassius' future ahead of his first professional fight. Bird is crushed to discover that Cash and the boys are making decisions without her, creating a rift in the family that jeopardizes their plans. With the fight around the corner, the Clay family must put aside their differences and do what's best for Cassius.

Sonny Liston emerges as a fearsome challenger in the boxing world, but fights to escape his ties to the mob. Cassius finds a trainer in the renowned boxer Archie Moore, but his confidence is tested when the legend is unimpressed. Unable to fit into Moore's rigid structure, Cassius is forced to decide between bending who he is or finding someone that believes in him to become the greatest.

Cassius climbs the ranks for a chance at the heavyweight title. Meanwhile, Sonny has bulldozed all competition and is closing in on Floyd Patterson fast. Inspired by an ostentatious wrestler, Cassius crafts a controversial new public persona. With it brings media attention and scrutiny into his private life that threatens to expose his growing ties to the Nation of Islam.

A newfound friendship with Malcolm X draws Cassius deeper into the Nation of Islam as he struggles to keep his faith hidden from his parents and the press. During a fraught visit home, Cash and Bird grow suspicious of their sons' religious beliefs. Back in Miami, Angelo scrambles to keep a controversial photograph out of the press that could threaten to derail Cassius' career.

Cassius follows his title dreams to London, where he faces British champion Henry Cooper. But his arrogance and Cooper's devastating left hook send him crashing to the canvas. With his title chance and the dreams of everyone who believes in him hanging in the balance, the world watches to see if Cassius can beat the count. Meanwhile, heavyweight champion Sonny tries to reshape his public image.

When word of Cassius joining the Nation of Islam hits the papers, public outcry puts the Heavyweight Title fight in jeopardy. His parents, trainers, cornermen, and even Malcolm X urge him to distance himself from the Nation of Islam so the fight can proceed. Cassius is forced to make an impossible decision that will define his career and his life.

Cassius faces heavyweight champion Sonny Liston in the fight of his career. As the brash contender taunts his formidable opponent, the pressure mounts to prove he's more than just talk. With his dreams in reach, the world watches with bated breath to see if Cassius will be the next Heavyweight Champion.