Miami, 1963. A young boy from Louisville, Kentucky, is on the path to becoming the greatest sportsman of all time. Cassius Clay is training in the 5th Street Gym for his heavyweight title clash against the formidable Sonny Liston. He is beginning to embrace the ideas and attitudes of Black Power, and firebrand preacher Malcolm X will soon become his spiritual adviser. Thus Cassius Clay will become 'Cassius X' as he awaits his induction into the Nation of Islam.

Cassius also befriends the legendary soul singer Sam Cooke, falls in love with soul singer Dee Dee Sharp and becomes a remarkable witness to the first days of soul music. As with his award-winning soul trilogy, Stuart Cosgrove's intensive research and sweeping storytelling shines a new light on how black music lit up the sixties against a backdrop of social and political turmoil - and how Cassius Clay made his remarkable transformation into Muhammad Ali.