Joe Louis plays a boxer like himself (except not as good), who becomes champion.
In Birmingham, Alabama Joe's mother Nora Thomas (Cleo Desmond) makes him wash. Her husband Jeff Thomas is brought home badly injured. Since his father no longer can walk, Joe says he will leave school to work.
Twelve years later Joe Thomas (Joe Louis) tells Mary Bowdin (Edna Mae Harris) that he is going away. His family gets money in the mail from him. Joe hitch-hikes and works washing dishes, meeting Crickie (Mantan Moreland). Joe and he work unloading. After a man hits Crickie, Joe knocks him out, losing his job. Joe fights in the Golden Gloves and wins the championship. At a nightclub Frankie Walburn (Clarence Muse) offers to manage Joe, who asks his mother. She says to be honest and fair. Singer Flora Bailey (Mae Turner) sees Joe training, and Frankie warns her. Joe's sister Eleanor Thomas (Marguerite Whitten) and Mary arrive and greet Joe. Flora with Duke Emerald (Jewel Smith) listens to Joe's fight. Duke gives her jewelry he won betting on Joe. Duke says he could make money if Joe would lose. Joe attends a banquet with Duke.
Frankie tells Nora and Mary that Joe is slacking off on his training. Joe goes out to hear Flora sing. Frankie heard that Duke is betting against Joe and argues with him. Mary goes to Flora and asks her not to hurt Joe's career. Joe watches dancing at a nightclub. Mary says good-bye to Nora and Eleanor. Joe is favored to defeat Baldwin but is knocked out. Frankie takes Joe out to eat. Frankie gives an older boxer money and tells Joe that he would not train. Nora tells Joe to start over.
Joe trains hard, but reporter Bob tells Frankie that Joe is missing a spark. Flora comes to the camp and asks Joe if he loves Mary, and he says he does. At the heavyweight championship match Flora tells Crickie that they can help Joe. During the fight they go to Mary and take her to the match. Joe is knocked down but is saved by the bell. After Joe sees Mary, he knocks down Stanley twice and wins. In the final scene Joe celebrates at a banquet with Frankie, Mary, and Crickie.
This story is similar to the early career of Joe Louis except that he never lost a professional fight until he was defeated by European champion Max Schmeling. Production Code director Joseph Breen warned the producers of this film its distribution in the South was questionable because it shows a black boxer defeating whites.