Fahrenheit 451 takes place in an unspecified future time in a hedonistic and rabidly anti-intellectual America that has completely abandoned self-control and bans the reading of books. Anyone caught owning them is, at the minimum, confined in a mental hospital and has the books confiscated and burned. At the maximum, the penalty is a sentence to immediate death. People are now only entertained by in-ear radio and an interactive form of television. The protagonist, Guy Montag, is a fireman, certain that his jobburning books, and the houses that hold them, and persecuting those who own themis the right thing to do.
It is by chance that one night he meets a girl named Clarisse McClellan, whose free-thinking ideals and liberating spirit cause him to question his life, his ideals, and his own perceived happiness; it is later claimed she has been killed in a car accident.
While ransacking the house of an old woman preceding its burning, Montag accidentally reads a line in one of her books: "Time has fallen asleep in the afternoon sunshine." This prompts him to steal a book. The woman then refuses to leave her house and her books, choosing instead to light a match she had concealed from the firemen's view, prematurely igniting the kerosene that they had doused around the house and martyring herself in the process. This disturbs Montag greatly.
While he is at home pretending to be sick and pondering his thoughts, he is visited by his fire Chief Captain Beatty, who elucidates for him the political and social reasons behind the existence of his occupation. Captain Beatty claims it was society, in its search for happiness, that brought about the suppression of literature through an act of self-censorship and that the totalitarian government acting as opportunists merely took advantage of the situation. Beatty says that all firemen are bound to steal a book at one time or another and that they can turn it in or burn it within 24 hours. Montag argues with his wife over the book, showing his growing disgust for her and for his society.
It is soon revealed that Montag has hidden dozens of books in the house, and he tries to memorize them so their contents can be preserved, but becomes frustrated that the words seem to simply fall away. He then remembers a man he had met at one time: Faber, a former English professor. Montag seeks Faber's help, and Faber begins teaching Montag about the general vagaries and ambiguities but overall importance of literature in the attempt to rationalize human existence. He also gives Montag a green bullet-shaped ear-piece so that Faber can guide him throughout his daily activities.
Montag returns to the fire house and gives Beatty a book. During a card game, Beatty tells Montag he had a dream about him, and relates the literary argument he says they had in his dream. He quotes many books and shows a thorough knowledge of literature, but he uses that knowledge to defend the firemen's role. Then there is yet another call to arms, and Beatty theatrically leads the crew to Montag's own home. He reveals that he knew all along of Montag's books, and charges Montag himself to destroy the house. Montag goes to work, but is not content only to destroy the books. He burns the televisions and other emblems of his ignorant past life. When Beatty realizes Montag has a compatriot in Faber, he threatens to track him down. Montag then burns and kills Beatty, knocks out two other firemen, and is soon pursued by the authorities for these crimes.
He flees to Faber's house, with a cybernetic hound and television network helicopters in pursuit, hoping to document his escape as a spectacle with the intent of distracting the people from the oncoming threat of war, a threat that has been forboded throughout the book. Faber tells him of vagabond book-lovers in the countryside. Then Montag, having washed off his scent in a local river, floats downstream and meets such a groupmostly older menwho, to Montag's astonishment, have memorized entire books, to be preserved orally until books are allowed again. They themselves burn the books they read to prevent them from being discovered; the true books are safely stored in their minds. The group leader, Granger, discusses the legendary phoenix and its endless cycle of long life, death in flames, and rebirth; he says the phoenix must be some relation of mankind.
At this point the war begins, and Montag watches helplessly as jet bombers fly overhead to attack the city. His wife, Mildred, is most probably killed. It is implied that the bombs are nuclear, a bitter irony that the world that sought to burn thought is burned itself. At the moment of the explosion, the stress and emotion of seeing the city burned causes key phrases from some of the books he has read to emerge from the depths of his memory. Montag then rejoins the group. The novel is concluded with a shocking but slightly optimistic tone. It is suggested that the society Montag knew has almost completely collapsed and a new society must be built from scratch. But there is doubt as to whether this new society may befall the same fate.