Having followed the career of world-famous boxing champion Joe Louis from the time he began fighting in Detroit, sportswriter Tad McGeehan sadly writes the story about his friend's final defeat in New York in 1951. His story begins in 1932, when Joe, known then as Joseph Louis Barrow, was a teenager living in Detroit: One day, while walking home from his violin lesson, Joe's pal, Johnny Kingston, talks him into using the money for his violin lessons to take boxing lessons. Though he comes home with a black eye after his first boxing lesson, Joe returns for more lessons, and soon shows great promise as a fighter. Joe's mother eventually discovers that he is not using the money she gives him for violin lessons, but she gives him her blessing to continue boxing when he promises to study it with all his heart. In 1934, after winning the Golden Gloves title in Detroit and Chicago, Joe is signed to a contract by manager Julian Black. In the same year, Joe begins training with Jack "Chappie" Blackburn, who puts him on a rigorous training program and teaches him the fighting techniques he will need to be a champion boxer. Following a string of winning fights, Joe returns to Detroit, where promoters Mike Jacobs and Johnson, who represent Madison Square Garden, compete for his contract. Joe shows little interest in the contract negotiations, as he is distracted by the beauty of Marva Trotter, a young woman from Chicago. Joe is introduced to Marva, and she tells him to look her up the next time he visits Chicago. After signing with Jacobs, Joe arrives in New York for his first fight there. A romance blossoms between Joe and Marva, and they are soon married. The wedding celebration is cut short, however, when Chappie reminds Joe that he must fight Max Baer. Joe wins by a knockout in the fourth round, then takes his earnings and goes on a wild spending spree. Joe's overspending soon leads to mounting debts, and his new cockiness eventually shows its ill effects in the ring. After a loss to German fighter Max Schmeling leaves Joe badly beaten, he shamefully admits that he did not do his best to prepare for the fight. He vows to resume his training and spends the next two years preparing for a re-match with Schmeling. Joe is further motivated to claim a victory over Schmeling when McGreehan tells him that Hitler is counting on Schmeling's win to support his theory of Aryan superiority. Joe finally gets his wish in June 1938, when he knocks out Schemling only minutes into their fight. Six years after their wedding, Marva, unable to bear being married to the big-time fighter, sues Joe for divorce. Joe, however, refuses to grant Marva a divorce, and instead works to repair their broken marriage. In the years that follow, Joe fights his way from one victory to another, and when war breaks out, he joins the Army as a private. Joe suffers an enormous loss when Chappie dies, and he names Mannie Seamon to replace him as his trainer. Following the war, Joe returns home to Marva and their new daughter, only to discover that he owes thousands of dollars in back taxes. Forced to return to the ring to pay his debts, Joe again loses the love of Marva, who files for divorce. After finally paying off his debts, Joe announces his retirement from the ring, but rumors soon circulate that he is planning a comeback. McGeehan urges Joe not to return, and tells him that he would only suffer embarrassing losses if he did. Joe ingores McGeehan's sage advice and, in 1951, returns to the ring for one last fight. Rocky Marciano's victory over Joe serves as the last episode in McGeehan's story about the champion fighter's career.