In a dystopian near future, after a second civil war, the American population is kept docile with TV news and drugs (self-administered as eye drops). A central committee rules everything. TV cameras are in every room and on the streets to monitor the population. In the city of Cleveland, a fireman (Montag) and his captain (Beatty) excel at their job, which is to hunt down rebels who collect books, particularly novels. When they catch such a rebel, they burn his books and erase his memory.
Montag begins to wonder why rebels do what they do, and he sneaks a forbidden book under his coat and into his apartment, where he begins to read it. (Somehow the general population knows how to read.) He follows a young rebel woman (Clarisse), and shows her the book to convince her that he's a rebel, too.
Meanwhile we see that Captain Beatty is an on-again, off-again rebel, too, and he sometimes helps, and sometimes hinders Montag as he explores the mysteries of the book world.
The Committee learns that the rebels have a plan to record the entire world's library of books into DNA, and spread the DNA throughout the world, so that the books will never be destroyed. But first the rebels have to get the DNA to Canada, where books are not being burned.
Clarisse takes Montag to the rebel hideaway, where the rebels reveal that the DNA has been implanted into a caged starling, and they tell him that they need to attach a tracking device to the bird so the Canadians can find it. Montag volunteers to bring them a suitable tracking device.
Montag returns to the fire station and sneaks a fire department tracking device into his pocket. (It's not explained why the Canadians would be able to track a bird using this device, but the fire department would not.)
Captain Beatty switches into his off-again rebel mode, and arrests Montag. Montag kills a fellow firemen, and runs away. Somehow Clarisse finds Montag in an alleyway, and they drive away towards the rebel hideaway.
But the firemen beat Montag and Clarisse to the hideaway, and they begin to burn it down. Montag sneaks into a burning barn, removes the bird from its cage, and begins to attach the tracking device. Beatty follows Montag, and confronts him, hesitating long enough for Montag to finish attaching the device and release the bird. The bird flies out through a hole in the barn roof.
Beatty incinerates Montag with his book-burning flame thrower. The bird flies over Lake Erie and into the wilds of Canada.