In the small town of Clanton, in fictional Ford County, Mississippi, a ten-year-old African-American girl named Tonya Hailey is violently raped by two neo-Confederates, James "Pete" Willard and Billy Ray Cobb, shortly after stealing a Confederate Flag from a local college exhibition. Tonya is later found and rushed to the hospital while Pete and Billy Ray are heard bragging at a roadside bar about their crime. Tonya's outraged father, Carl Lee Hailey, consults his friend Jake Brigance, a white attorney who had previously represented Hailey's brother, on whether he could get himself acquitted if he killed the two men. Jake tells Carl Lee not to do anything stupid, but admits that if it had been his daughter, he would kill the rapists. Carl Lee is determined to avenge Tonya, and while Pete and Billy Ray are being led into holding after their bond hearing, he kills both men with an M16 rifle.
Grand Dragon, Stump Sisson. Subsequently, the KKK attempts to plant a bomb beneath Jake's porch, leading him to send his wife and daughter out of town until the trial is over. Later, the KKK attacks Jake's secretary, Ethel Twitty, and kills her frail husband, Bud. They also burn crosses in the yards of potential jurors to intimidate them. On the day the trial begins, a riot erupts between the KKK and the area's black residents outside the courthouse; Stump is killed by a Molotov cocktail. Believing that the black people are at fault for Stump's death, the KKK increase their attacks. As a result, the National Guard is called to Clanton to keep the peace during Carl Lee's trial. The KKK shoots at Jake one morning as he is being escorted into the courthouse, missing Jake but seriously wounding one of the guardsmen assigned to protect him. Soon after, Ellen Roark is abducted and assaulted. They burn down Jake's house. During trial deliberations, the jury's spokesman is threatened by a KKK member with a knife. Eventually, they torture and murder "Mickey Mouse", one of Jake's former clients who had infiltrated the KKK and subsequently gave anonymous tips to the police, allowing them to anticipate most KKK attacks.
Despite the loss of his house and several setbacks at the start of the trial, Jake perseveres. He badly discredits the state's psychiatrist by establishing that he has never conceded to the insanity of any defendant in any criminal case in which he has been asked to testify, even when several other doctors have been in consensus otherwise. He traps the doctor with a revelation that several previous defendants found insane in their trials are currently under his care despite his having testified to their "sanity" in their respective trials. Jake follows this up with a captivating closing statement.
On the day of the verdict, tens of thousands of black citizens gather in town and demand Carl Lee's acquittal. The unanimous acquittal by reason of temporary insanity is only achieved when one of the jurors asks the others to seriously imagine that Carl Lee and his daughter were white and that the murdered rapists were black. Carl Lee returns to his family and the story ends with Jake, Lucien and Harry Rex having a celebratory drink before Jake holds a press conference and leaves town to reunite with his family.