The novel opens with a father and son sleeping outside in the cold. The father awakens from a dream of him and his child in a cave facing a huge, nameless creature that eventually runs away into the dark. At dawn, the father (who, along with the son, remains nameless throughout the novel) surveys the landscape, trying to decide where they will travel next. He is unsure of the month or the day because “he hadn’t kept a calendar for years.” The scene before him reveals ash from a post-nuclear holocaust falling from the sky and drifting across the landscape. The father and son are survivors, fighting to live in a world that has been destroyed by nuclear bombs and ravaged by chaos and confusion.

The boy awakens, and they set off on their journey, following a road through the countryside. A grocery cart and knapsacks contain all of their belongings. There is a pervasive sense of danger, and they are constantly on the alert. Discovering an old, abandoned gas station, they explore the remains, hunting for food or other useful items. They find some motor oil and siphon it off to use in their only lamp. That night, at camp, the father reveals that they are heading south because it will hopefully be warmer there.

The boy and his father travel south for “days and weeks to follow,” with not much break during the monotonous journey. They suffer from an endless “nuclear winter”—rain, snow, and bitter cold. The father has flashbacks to his childhood home, to fishing with his uncle, and to his wife, who likely killed herself because she could not bear living in such a dreary world. He also dreams, and when the dreams are pleasant, happy ones, he worries, feeling that bad dreams are normal but happy ones are “the call of . . . death.” He believes that his dreams, if pleasant, are harbingers of death to come. Weak and afflicted with a cough, he worries that if he dies, he will leave his son behind to fend for himself. He also worries constantly about shoes, shelter, food, and the unnamed danger, which the reader eventually learns is packs of barbaric survivors who have turned to cannibalism. The father and son carry a single gun with only three bullets as protection against those who hunt and kill any other survivors for food.

Along the road, they scavenge for blankets, canned food, and other useful goods from abandoned houses, grocery stores, barns, and sheds. The father at one point finds a can of Coca-Cola and gives it to the boy to try, who has never tasted the soft drink. They pass the house where the father grew up, and they walk through; however, the son is very afraid of being there. He is worried that there are people living inside that might harm them and that being there makes them conspicuous targets. They leave and travel to waterfalls the father knew of as a child, then continue onward along the road.

Throughout their travels, the father continues to have flashbacks to the first bombs, to his wife and her struggles to survive as the “walking dead in a horror film,” and to his childhood life. Readers learn that his wife had their baby after the bombs and that the boy has grown up his entire life in this post-nuclear world. The father tries to describe the world before the bombs, and the boy enjoys listening to the tales, asking many questions. They do not speak often of the boy’s mother but occasionally reference her when speaking of death. When the boy at one point mentions that he “wants to join her,” the father chastises him, telling the boy to never say that again.

On their journey, the father and son have several encounters with dangerous groups of cannibals. The first incident comes as they are sleeping near the road; they see a crowd of people coming, armed with clubs and pipes. They try to run, but one barbarian walks right into them. The father is forced to shoot the man, and although they manage to escape, they have to abandon the cart, which is then ransacked, leaving the father and son without any supplies. Later in the novel, they see another gang of cannibals passing on the road; they have slaves and many supplies; the father and son manage to hide and not be seen.

Another encounter with these dangerous people occurs as the father and boy come up to a house that they think is abandoned; however, they quickly realize that it is occupied by the cannibals. In the basement are prisoners, chained and partially maimed, as the cannibals have taken body parts to eat. They again quickly leave without being seen. In another horrifying instance, they encounter a few people, including a pregnant woman, only to come across their empty camp the following day, with the remains of a newborn infant charred over the fire. These brief encounters make deep impressions on the young boy; he is often afraid, has nightmares, and is wary of buildings and other people.

They do run across the occasional nonbarbaric survivor just trying to survive, struggling to find normal food like they are, and each time, the boy is moved to help. They meet one man who is shuffling along at a slow pace. The father guesses he has “been struck by lightning.” The boy wants to stop and help, but the father insists that there is nothing that they can do for the man and that he will die. The boy is distressed and upset at this, and they both speak of it for days to come, the father trying to convince him that it was okay to leave the man, that there was nothing to be done.

Another time they come across a ninety-year-old man, whom they travel with for a few days. They give him food and ask him questions; the man’s responses are guarded and ambiguous. He hints that there are other “good” survivors out there and that groups of them have fed him and taken care of him before. The father questions him about this, but the old man takes back what he has said, refusing to give out any more information. The father and son argue for days about what to do with the old man, whether to keep him as their companion traveler or to leave him behind. The son has an innate desire to reach out and group together, to help others survive. The father discourages this, explaining that taking on people will slow them down, make them more vulnerable to attack, and deplete their food reserves. They end up leaving the old man behind, to the boy’s dismay, and the father struggles to convince him that it is for their own good and for their own survival that they must do so.

At one point they find an underground bunker filled with food and supplies. They stay there for a few days, eating and sleeping, but unfortunately, they cannot stay because it is too dangerous. If they were discovered, their lives would be at risk. They eventually make it to their destination—the ocean, in the south—only to discover that it is no warmer than anywhere else, with no more shelter or food. They scavenge a shipwrecked ocean liner, but as they are doing so, they discover that someone has ransacked their cart and all of their supplies; they follow the culprit’s tracks in the ash and confront him. The father, using his gun as a threat, takes back all of their belongings and leaves the man, naked, standing alone. Later, the father sees a man in the distance, shooting an arrow at them. He ducks for cover with his son but is hit in the leg. Eventually, they move on, going along the coast, scavenging as they can.

The father becomes afflicted with a cough that gets progressively worse, and eventually he is overwhelmed by the illness. The boy takes over hunting for food and tries to revive his father, to no avail. The father perishes during the night.

The boy is now left on his own. He tries to gather his things and formulate a plan, but as he does so, he is approached by a man who turns out to be kind, one of the “good guys.” He is the father of a family that is living in hiding. The man helps the boy leave his father’s body, takes the boy into his own family, and readers are left assuming that he will continue his quest for survival with them.