There is no singular main plot in the play Fences, as the focus is more on the characters' inner lives than any big events. The plot is best described as a character study of the main character, Troy Maxson, as he butts heads with his son and experiences marital fallout once his affair with another woman is revealed to his wife.
An overarching issue for Troy is his relationship with and expectations for his son Cory. Cory has a job at the A&P, but he has been given the chance to play college football. Troy once had athletic dreams, too, but racist attitudes prevented him from being accepted into the major leagues. He feels the college will drop Cory from the team because of his skin color and he does not want Cory to have his own hopes dashed in the same way his were. This creates conflict between father and son, resulting in Cory leaving the house and eventually joining the Marines. When Troy dies, Cory does not wish to attend his funeral.
Troy's affair with another woman is another major component of the plot. When Troy's mistress dies in childbirth, he and his estranged wife Rose take his infant daughter in as their own. However, the infidelity creates a strain in Troy's marriage. Ultimately, the plot is driven by Troy's tragic character flaws and all of the problems they create within his relationships.