One of the major climaxes in the novel occurs in Part Three. Mildred is gone and Beatty is forcing Montag to burn his own house. With the absence of his wife, destruction of his house, and the seeming end to his days as a fireman, Montag's old life is effectively gone as well. Instead of handing the flame-thrower over to Beatty and bowing to authority, he turns it on Beatty and kills him, thus destroying his most intimate authority figure. Montag then turns on the firemen, making his transformation complete: from burning books to burning the burners (firemen).
The second climax occurs when Montag reaches the river and is then out of reach of the authorities and out of range of the new and improved Mechanical Hound. Floating peacefully down the river, the climax complete, he literally leaves the story en route to a new one:
He felt as if he had left a stage behind and many actors. He felt as if he had left the great seance and all the murmuring ghosts. He was moving from an unreality that was frightening into a reality that was unreal because it was new.