Mr. Morrison is a character who comes home with Cassie's father. Papa says that he is going to stay on to help them out for awhile and that he'll be paid with room, board, and a little money. Mr. Morrison explains that he lost his job when he got into a fight with some white men. He says it was their fault but that they weren't fired. Cassie's mother says that he's glad nothing worse happened and welcomes him.
This foreshadows what happens with T. J. Avery later in the book. He begins spending time with two white men who are troubled and lead him into danger. Though he's more than willing to commit small crimes, he's not the kind of person to kill someone. When the two men he spends time with kill a shop owner, they frame him for the crime. Because he is black and the other two are white, no one believes him.
Mr. Morrison's story foreshadows T. J.'s fate. In the book, a black person cannot stand up against a white person and be believed by the white community. The trouble with that is that the justice system and businesses are owned by white people in the book. So T. J. finds himself facing the prospect of being hung for a crime he didn't commit even though the people accusing him are known criminals. It is because he's black and they're white.