The novel's protagonist, Guy Montag, takes pride in his work with the fire department. A third-generation fireman, Montag fits the stereotypical role, with his "black hair, black brows…fiery face, and…blue-steel shaved but unshaved look." Montag takes great joy in his work and serves as a model of twenty-fourth-century professionalism. Reeking of cinders and ash, he enjoys dressing in his uniform, playing the role of a symphony conductor as he directs the brass nozzle toward illegal books, and smelling the kerosene that raises the temperature to the required 451 degrees Fahrenheit — the temperature at which book paper ignites. In his first eight years of employment, Montag even joined in the firemen's bestial sport of letting small animals loose and betting on which ones the Mechanical Hound would annihilate first.
In the last two years, however, a growing discontent has grown in Montag, a "fireman turned sour" who cannot yet name the cause of his emptiness and disaffection. He characterizes his restless mind as "full of bits and pieces," and he requires sedatives to sleep. His hands, more attuned to his inner workings than his conscious mind, seem to take charge of his behavior. Daily, he returns to a loveless, meaningless marriage symbolized by his cold bedroom furnished with twin beds. Drawn to the lights and conversation of the McClellan family next door, he forces himself to remain at home, yet he watches them through the French windows.
Through his friendship with Clarisse McClellan, Montag perceives the harshness of society as opposed to the joys of nature in which he rarely partakes. When Clarisse teases him about not being in love, he experiences an epiphany and sinks into a despair that characterizes most of the novel. He suffers guilt for hiding books behind the hall ventilator grille and for failing to love his wife, whom he cannot remember meeting for the first time. But even though he harbors no affection for Mildred, Montag shudders at the impersonal, mechanized medical care that restores his dying wife to health.
Montag's moroseness reaches a critical point after he witnesses the burning of an old woman, who willingly embraces death when the firemen come to burn her books. His psychosomatic illness, a significant mix of chills and fever, fails to fool his employer, who easily identifies the cause of Montag's malaise — a dangerously expanded sensibility in a world that prizes a dulled consciousness. Lured by books, Montag forces Mildred to join him in reading. His hunger for humanistic knowledge drives him to Professor Faber, the one educated person that he can trust to teach him.
Following the burning of the old woman, his company's first human victim, Montag faces an agonizing spiritual dilemma of love and hate for his job. As a fireman, he is marked by the phoenix symbol, but ironically, he is inhibited from rising like the fabled bird because he lacks the know-how to transform intellectual growth into deeds. After he contacts Faber, however, Montag begins a metamorphosis that signifies his rebirth as the phoenix of a new generation. A duality evolves, the blend of himself and Faber, his alter ego. With Faber's help, Montag weathers the transformation and returns to his job to confront Captain Beatty, his nemesis. Beatty classifies Montag's problem as an intense romanticism actualized by his contact with Clarisse. Pulled back and forth between Faber's words from the listening device in his ear and the cynical sneers and gibes of Beatty, who cites lines from so many works of literature that he dazzles his adversary, Montag moves blindly to the fire truck when an alarm sounds. Beatty, who rarely drives, takes the wheel and propels the fire truck toward the next target — Montag's house.
When Beatty prepares to arrest him, Montag realizes that he cannot contain his loathing for a sadistic, escapist society. Momentarily contemplating the consequences of his act, he ignites Beatty and watches him burn. As Montag races away from the lurid scene, he momentarily suffers a wave of remorse but quickly concludes that Beatty maneuvered him into the killing. Resourceful and courageous, Montag outwits the Mechanical Hound, but impaired by a numbed leg, he is nearly run over by a car full of murderous teenage joyriders. With Faber's help, he embraces his budding idealism and hopes for escaping to a better life, one in which dissent and discussion redeem humanity from its gloomy dark age.
Baptized to a new life by his plunge into the river and dressed in Faber's clothes, Montag flees the cruel society, which is fated to suffer a brief, annihilating attack. The cataclysm forces him face down onto the earth, where he experiences a disjointed remembrance of his courtship ten years earlier. Just as his leg recovers its feeling, Montag's humanity returns. After Granger helps him accept the destruction of the city and the probable annihilation of Mildred, Montag looks forward to a time when people and books can again flourish.