Dr. Perceval makes a house call to the Gregg estate in the company town of Graniteville, South Carolina. William Gregg, the owner of the town cotton mill, is declared dead after a lingering illness. The doctor and Mrs. Gregg then visit the home of Patrick McEvoy, a gardener employed by the Greggs, to tend to his son Robert McEvoy, whose leg had earlier been broken in an industrial accident that some suspect James Gregg, William's son, may bear responsibility for. Seeing the leg has become badly infected, Mrs. Gregg persuades Robert to consent to amputation. William Gregg is buried in a well-attended ceremony with an adulatory eulogy.
Robert, now fitted with a prosthetic leg and crutch, takes a job sweeping up at the mill. A group of impoverished people come by train to Graniteville seeking work, but James, now the mill's owner, turns them away. Over supper, with Robert absent, the McEvoys discuss his perplexing, troubled nature. Mrs. Gregg and James visit the grave of an unnamed boy who died visiting Graniteville in 1855. James chides his mother for her paternalistic concern for the poor. Martha McEvoy, a 14-year-old who works spinning cotton, goes looking for Robert and finds James, who makes lewd remarks and offers to pay her a gold piece, prompting her to flee. Mr. Giles, an assistant at the mill, finds Patrick in his glasshouse and inquires after Robert, who has been absent from work. Patrick answers that he does not know his son's whereabouts.
Some time later, Martha McEvoy writes a letter to Robert telling him that
> "mama has took sick again"
and that she and her father wish he would return home. Robert hops off a horse-drawn cart and drives away two black gravediggers when he discovers they are burying his mother, who he says
> don't belong to the mill.
Robert finds his father's glasshouse barren and learns he is no longer employed as a gardener. That night Robert drinks whiskey and commiserates with employees of the mill, including Pinky. The next morning, Robert wakes up in a barn. As Patrick starts his shift at the mill, he learns his son has returned. Robert confronts James in his office. After an argument ensues, James surmises that Robert is there begging for money and offers him a gold piece. Robert draws a pistol. James reaches for a desk drawer. Robert shoots him in the stomach and exits the mill. James stumbles outside and fires at Robert, missing. Robert returns fire, killing James. Patrick and other mill employees walk outside.
Robert stands trial, accused of murder. The prosecutor reads an opening statement before a majority-black jury. Mr. Giles and another witness testify. After trial, Robert's attorney O. C. Jordan speaks with a discouraged Patrick, telling him that he is confident Robert will go free, and that it would be unwise for Robert to testify as doing so would risk an unpopular sullying of the Gregg name. Jordan also reveals that the defense has agreed with Mrs. Gregg to avoid calling any female witnesses. A constable asks Patrick to return home to console his wife. Starks Sims, a boy who works for Mr. Giles, testifies that he witnessed Robert shoot James. W. J. Whipper, a black attorney for Robert's defense, cross-examines Starks; Whipper asks if Starks had ever read any notes written by James to any female employees of the mill. Starks replies that he had never done so because he is illiterate. That night, Patrick goes to ask Whipper to have Robert testify and Whipper responds that it would not be possible because of Robert's erratic nature, but reassures Patrick and counsels him about the limitations of the law.
At trial, Robert is sentenced to death. Martha goes to Mrs. Gregg, apparently to plead her brother's innocence, but then tells Mrs. Gregg that James "never done nothing" to her. Believing Martha is there to console her, Mrs. Gregg takes ease and asks her servant Daphne to bring tea. Martha says that the Greggs "must have failed him somewhere". Enraged, Mrs. Gregg orders her to leave.
Robert poses in a studio for a portrait photograph taken, seated, from the waist up, taking care that his legs not be shown. The photographer asks if copies might be made to print for sale, with half of the proceeds to go to his family. Robert replies that he does not mind if people are ignorant enough to buy his image, but does not want his family to know where any proceeds are sent from. In the street, Martha encounters Robert, who says he was never meant to be hanged and should have gone to the penitentiary. Martha says she would have testified and told "any kind of lie" in his defense. Robert tells her to forget she had a brother and to find the best man she can and make him treat her right. Robert is executed by hanging. Dr. Perceval declares the time of death. Patrick takes his son's body in a coffin onto a cart and rides away.
