In a Louisiana penitentiary during the Great Depression, Paul Edgecomb is a death row corrections officer who oversees inmates awaiting their execution on "The Green Mile," so named because of the green linoleum that lines the floor. The routine of grim responsibilities weighs heavily on Paul and his team of guards, who are seasoned to the harsh realities of their work, which includes facilitating the final walk of condemned men. Their lives take an unexpected turn with the arrival of a gigantic black man named John Coffey, convicted of the violent rape and murder of two young white girls—a crime that his simple-minded demeanor and gentle nature seem to contradict.

Coffey displays extraordinary, supernatural abilities that defy explanation and deeply affect Paul and the other guards. As bizarre incidents unfold on the mile, Coffey forms a special bond with the empathetic Paul, who starts to question the morality of his occupation and whether justice is truly being served. While dealing with the daily dramas of life on the block, including the arrival of a dangerous and delinquent new inmate and the personal struggles of his colleagues, Paul is forced to confront his own moral compass as he learns more about Coffey's mysterious gift, and the profound impact it has on those around him.