Jefferson is very much in the wrong place at the wrong time and witnesses a robbery-murder at a liquor store. He is convicted of murder and sentenced to death by electrocution. In his trial his defense lawyer compares him to a hog that isn't worth killing.
His aunt, Miss Emma, asks the teacher, Grant Wiggins, to visit Jefferson in prison and make him into a man, so that he knows he isn't a hog. Grant is dead set against the idea, but his aunt Lou is dead set on his going. She wins, as per usual.
Lou (aka Tante Lou) forces Grant to go with her and Miss Emma to the Pichot's house, the rich, white folks who own the plantation. Miss Emma and Lou used to work for the Pichots as cooks and housekeepers, and when Grant left for college Lou was proud to tell him that she didn't have to work anymore. However, Grant finds himself marching up the back steps of the house to the door reserved for servants (white people use the front door) to ask for a favor. He finds it humiliating and is angry with Lou for making him do it.
Henri Pichot's brother-in-law is the sheriff, and after some convincing he agrees to talk to the sheriff to ask for permission to let Grant visit Jefferson. So at least the humiliating visit has a purpose.
The visits with Jefferson are tough, because he is pretty much nonresponsive. Miss Emma and Grant visit him a few times, always with a basket of food. He ignores them and the food. Finally, Miss Emma sends Grant alone because she says she is too sick to go. Grant is sure that Miss Emma is faking and that it was a plan all along to get him to go to the jail alone.
At the courthouse, during Grant's first one-on-one visit, Jefferson acts like a hog. He says that he's being fattened up to be killed for Christmas dinner, and eats by sticking his head in the bag (look, Ma, no hands!). Grant is upset and doesn't know what to tell Miss Emma about his visit, so he avoids her. When he finally does see her he just says that Jefferson is "all right." Miss Emma smells a rat, and she knows that she was right when she visits Jefferson herself. He calls himself a hog then, too, and Miss Emma is horrified.
Jefferson's execution date is set, and afterward he starts acting calmer. In fact, he even tells Grant to thank the schoolchildren for sending him pecans at the jail. This is his first sign of acting like a human being with feelings, and Grant is overjoyed.
Grant heads to a bar, excited to tell his girlfriend, Vivian, about his breakthrough with Jefferson. Instead, he gets into a knockdown, drag-out fight with some bricklayers who are shooting off their mouths about Jefferson. Not exactly the romantic date Grant had planned.
On his next trip to visit Jefferson, Grant gives him a radio and a notebook to write down his thoughts. This is a huge deal for Jefferson, because the radio gives him a connection to the outside world, and the notebook allows him to, for the first time, reflect and put his thoughts on paper.
Jefferson's execution day finally arrives, and Grant refuses to be in the room to witness. Back at the school, he has his students kneel to pray until they hear that Jefferson is dead, and Grant takes off for a walk. Sitting under a pecan tree, he sees a butterfly and takes it as a sign that it's all over for Jefferson. A deputy arrives to give Grant the news that Jefferson walked on his own two feet, like a man, at the execution. When Grant goes in to tell the students, he cries.