Sling Blade is the story of Karl Childers, a metally-retarded man, who was institutionalized as a child for killing his mother and her lover. Karl felt that he was protecting his mother from harm, but when he realized that she was wanting sex, he killed her, too. As the film begins, he is getting out of the institution and going back to the real world.

Karl moves back to his old town where the head of the hospital helps him find a job. Karl becomes friends with a young boy named Frank and his mother, Linda. Linda's boyfriend, Doyle, is cruel, and Linda cannot stand up to him. Karl cares for them and when Doyle decides to move in permanently, Karl realizes he must take action. Karl murders Doyle in order to protect Frank and Linda. In the final scene, we see Karl sitting in the institution once...