In a dystopian America, a major source of entertainment is the Long Walk, in which 100 teenage boys walk without rest along U.S. Route 1. Each Walker must stay above four miles per hour. If a Walker drops below this speed for 30 seconds, he gets a warning. A Walker can lose a warning if he walks for an hour without getting another warning. If a Walker gets three warnings and continues to lag behind for 30 seconds, he is shot dead by soldiers. The last surviving Walker earns a large sum of money and a "Prize" of his choice.
Ray Garraty from Androscoggin County, Maine, arrives at the start of the Walk on the Canada-Maine border, where he meets several other Walkers such as the sardonic McVries, the friendly Baker, the cocky Olson and the enigmatic Stebbins. The Major, the leader of the secret police force known as the Squads, starts the Walk. Throughout the first day, Garraty befriends Baker, Olson, and several other Walkers such as Abraham and Pearson, growing particularly close to McVries and becoming particularly intrigued by Stebbins. A Walker named Barkovitch reveals to a reporter that he is in the Long Walk to "dance on the graves" of other participants, and later provokes another Walker into attacking him, resulting in the Walker's death and Barkovitch being ostracized.
Garraty succeeds in surviving the night. Scramm, the odds-on favorite in Vegas, tells Garraty that he has a pregnant wife and so will have sufficient motivation to keep going. Garraty decides that his motivation will be surviving until Freeport as this will allow him to see his girlfriend Jan in the crowd. The Walkers begin to resent the Major, and McVries stops walking in an attempt to fight the soldiers, but is saved by Garraty. In return, McVries saves Garraty's life after Garraty experiences hysterics when the spectators increase in number. This camaraderie infuriates Olson, who is now severely fatigued and wants Garraty to die. Garraty reveals to the others that his father was Squaded, and a fight almost breaks out between McVries and another Walker, Collie Parker, when Parker claims that only "damn fools" are Squaded.
Stebbins tells Garraty both that he believes he is going to win, and that the Walkers are all participating because they want to die. McVries and Baker both seem to be examples of this, due to McVries seeking pain and Baker's fascination with death; McVries also tells Garraty that he will sit down when he cannot walk any further. Stebbins also advises Garraty to watch Olson, who keeps walking despite being unresponsive. After Garraty brings Olson out of this state, Olson attacks the soldiers and is killed slowly and brutally.
Scramm catches pneumonia and becomes unable to finish the Walk, and the other Walkers agree that the winner should provide financial security for Scramm's wife. Garraty asks Barkovitch to join the agreement, and Barkovitch agrees as he has become lonely and manic in his isolation from the others. Garraty also asks Stebbins, who tells Garraty that there was nothing special about Olson and that he was lying; Garraty, however, believes that Stebbins came to a realization that scared him. Scramm thanks the others and is killed in an act of defiance against the soldiers.
After developing a charley horse, Garraty is given three warnings and has to walk for an hour to lose one. To distract himself, he tells McVries about how he felt a compulsion to join the Walk and that his mother was blinded by the thought of financial security. McVries reveals that he joined the Walk against the wishes of his family, and Abraham tells Garraty that he did not withdraw after being accepted due to the amusement it provided his town.
Garraty begins to suffer from doubts about his sexuality and masculinity due to suppressed memories re-emerging, especially after McVries hints that he is sexually attracted to Garraty. This causes Garraty to lash out at a deteriorating Barkovitch, and Barkovitch commits suicide when the rest of the Walkers begin taunting him. Garraty wakes the next morning to find that many Walkers (including Pearson) have died overnight, as Barkovitch predicted.
When the Walkers arrive in Freeport, Garraty attempts to die in Jan's arms but is saved by McVries. As a response, Abraham convinces the Walkers to make a promise to stop helping each other, which Garraty does reluctantly. This has disastrous consequences: Parker starts a revolution against the soldiers but is killed when nobody joins in; Abraham removes his shirt and catches pneumonia overnight because nobody can offer him a replacement, resulting in his death; Baker falls over and gains a severe nosebleed, and is given three warnings as nobody can help him up.
On the morning of the fifth day, Stebbins reveals to Garraty and McVries that he is the Major's son, and that his Prize would be acceptance into the Major's household. However, Stebbins has become aware that the Major is using him as a "rabbit" to cause the Walk to last longer, which has worked, as seven Walkers make it into Massachusetts. Baker, now somewhat delirious and described as a "raw-blood machine", tells Garraty that he cannot walk any further and thanks Garraty for being his friend. Garraty unsuccessfully tries to talk him out of suicide.
With Baker dead, the only remaining Walkers are Garraty, Stebbins and McVries. As Garraty tells him a fairy tale, McVries falls asleep and begins walking at the crowd, and Garraty breaks his promise and saves him; however, McVries chooses to sit down and die peacefully. A distraught Garraty is beckoned by a dark figure further ahead, and decides that he will give up because Stebbins cannot be beaten. When he tries to tell Stebbins, Stebbins clutches at him in horror and falls over dead. His corpse is shot when the Major arrives.
This leaves Garraty the uncomprehending winner. He ignores the Major and approaches the dark figure (whom he believes to be another Walker), declaring that there is "still so far to walk". Garraty begins running after the figure.
