Set in the twenty-fourth century, Fahrenheit 451 introduces a new world in which control of the masses by the media, overpopulation, and censorship has taken over the general population. The individual is not accepted and the intellectual is considered an outlaw. Television has replaced the common perception of family. The fireman is now seen as a flamethrower, a destroyer of books rather than an insurance against fire. Books are considered evil because they make people question and think. The people live in a world with no reminders of history or appreciation of the past; the population receives the present from television.
Ray Bradbury introduces this new world through the character Guy Montag, the protagonist, during a short time in his life.
The story begins with an inciting incident in which Montag meets Clarisse McClellan. Montag, a fireman who destroys books for a living, is walking home from work one day when the young Clarisse approaches him and introduces herself. Clarisse is the antithesis of anyone Montag has ever met. She is young, pretty, and energetic, but more importantly, she converses with him about things that he has never considered. Her inquisitive nature fascinates him because she ponders things such as happiness, love, and, more importantly, the contents of the books that he burns.
At first, Montag tries to ignore her questions, but on the rest of his walk home, he cannot get the young girl out of his mind. Upon entering his home, however, her image is quickly erased. Montag enters his bedroom to find an empty bottle of sleeping pills lying on the floor next to his bed. He discovers that his wife Mildred (Millie), whether intentionally or unintentionally, has overdosed on the pills. He calls the emergency squad, and the strangers come with their machine to save his wife.
The next morning, Montag attempts to discuss what happened the night before, but his wife is uninterested in any type of discussion. She avoids Montag's questions and instead focuses on the new script she has received for an interactive television program. Montag, though frustrated and confused about what happened the previous night, heads off to work.
On his way to work, Montag again encounters Clarisse and is left pondering things like the taste of rain and what dandelions represent.
He enters the fire station and immediately encounters the Mechanical Hound, who actually growls at him. Because of this brief encounter, Montag realizes that the Hound doesn't like him, a point that he quickly points out to his fellow fireman, Captain Beatty.
Several days pass since Montag's last meeting with Clarisse. During one of his final conversations with Clarisse, Montag learns that she fears the violence in her peers. She points out that their world used to be an entirely different world, one where pictures showed actual people and people talked about important things.
One day at the fire station, the firemen receive a call that an old woman has stashed books in her house. The firemen race to her home and begin destroying the contraband. Montag urges the woman to leave the house because the entire home will be destroyed, but she refuses to leave her precious books. The home, along with the old woman and her books, is set aflame, but not before Montag steals one of the books.
Later the same night, Montag tries to discuss the day with Millie, but she is not interested in what he has to say. During their conversation, Montag discovers from Millie that Clarisse was killed in an automobile accident.
Montag decides to call in sick to work the next day, but he is surprised by a visit from Beatty. Somehow, Beatty knows that Montag is keeping a book, and he is interested in reading it. Beatty converses at great length with Montag and tells him that every fireman gets the itch to read a book at some point in his career. Beatty also tells Montag that even though he may keep the book for twenty-four hours, he must return to work, with book in hand, so the book can be properly destroyed.
After this meeting, Montag shows Millie that he has been hiding, not just one book, but a cache of books in the house for some time. He then convinces Millie to sit and read the books with him. While reading, Montag attempts to converse with Millie about the content of the books but finds that she cannot comprehend, nor does she want to comprehend, what they are reading.
At this point, Montag remembers an old, retired English professor, Faber, whom he had met in a park. Montag decides to visit Faber to gain more understanding about books and his recurrent thoughts.
Upon reaching Faber's house, Montag is first greeted by the old man with fear. Faber worries that Montag has come to burn his books and home, but he is quickly pacified when he sees Montag's Bible and hears that Montag wants to talk with him. During their conversation, Faber agrees to teach Montag, and he gives Montag a seashell radio so they can communicate with one another.
Montag returns home to find Mrs. Phelps and Mrs. Bowles, two of Millie's friends, at his home. Feeling especially courageous, Montag decides to enlighten them by reading "Dover Beach," but instead, he causes problems for himself because he scares the women. They flee the house in tears, and Millie is angry with him for causing the scene.
With Faber still speaking in his ear, Montag returns to work and gives Beatty a book, which is promptly incinerated. After a lengthy discussion with Beatty, an alarm comes into the station, and the firemen rush to destroy the next house. When the firemen stop in front of the unfortunate house, Montag is surprised to see his own home.
Promptly, Beatty orders Montag to destroy his home and places him under arrest. Montag takes a perverse pleasure in destroying the home, especially the television, and in the following moments, he also kills Beatty with his flamethrower. The Mechanical Hound attacks Montag before he can escape, but he destroys it with fire before the Hound can destroy him.
Montag runs to Faber's home for protection but quickly realizes that he is endangering Faber. Thus, he stops at the home of Black, a fellow fireman, and hides the books inside the house to incriminate him. Montag then reaches Faber's home, and Faber tells him to escape down the river because another Mechanical Hound is on the search for him.
After helping Faber rid all trace of him, Montag races toward the river in hopes of escaping the search. By the time the Mechanical Hound reaches the river, Montag's trail is lost. He safely floats down the river toward a group of social outcasts and criminals like himself.
Montag leaves the river and immediately finds the group that Faber told him about. He meets the unacknowledged leader of the group, Granger, who welcomes Montag to join them. Although he thought that the search was called off, Montag finds out that it was just rerouted. He watches on television as an innocent man, strolling along the city streets, is purposefully identified as Montag and is killed for the entire television audience to see.
The group decides to move on from their current site, and while they are walking, Granger explains the purpose of the outlaw group: They are preserving books by memorizing their contents and then destroying them. Books can not be forgotten, because each person in the group is a living version of them. Montag becomes the Book of Ecclesiastes from the Bible.
As the men continue in their journey, Montag and Granger watch as bombs fall upon the city and destroy everything in their path. The final war has begun. Although the men are escaping the city, they decide, without discussion, to return to the city with Montag in the lead.