In the beginning, Montag believes that the world he lives in is the right way to leave. Not only that, but he takes pleasure in doing things that should be illegal, just like the rest of the population. He thinks it is "a special pleasure to see things eaten, to see things blackened can changed. (page 1, online)" In this stage, Montag is innocent, yet guilty of many crimes.
Montag Becomes a Student
Next, Montag meets a girl named Clarisse. She knows that it's important to ask questions, especially in the world they live in. "'Are you happy? (page 7, online)'" is a question she asked him once, for example. Although he was confident he knew everything he needed to know, he had never thought to ask himself a question like that before. Clarisse made Montag begin to think for himself and question why things were the way that they were.
Towards the middle, Montag steals a book from one of the houses he burned. He has to skip work because he feels guilty and confused about why he did it, but he knows there is something he needs to know about the world he lives in. His fire chief, Beatty, and tries to convince Montag that "'thanks to [technology], you can stay happy all the time (page 42, online)'". He basically tells Montag to stop thinking differently and go back to obeying orders without question. Montag gets very frustrated.
Montag Finds Fulfillment
Later, Montag finds a man named Faber, who gives him direction on what to do with the knowledge he now has about the world. Faber gives him advice and help. For example, Faber told Montag, "'those who don't build must burn. It's as old as history and juvenile delinquents.' (page 62, online)" Montag becomes confident that, somehow, it is his job to basically save the world from destroying itself.
Next, Beatty finds books that Montag has been hiding in his house and forces Montag to burn his own house down. Afterwards, Montag takes the final step into becoming a full - blown criminal. "Beatty, he thought, you're not a problem now (page 82, online)", thought Montag after he killed Beatty. Montag is angry and passionate about his books, and does not plan on giving up without a fight.
Lastly, at the end of the book Montag flees the city just in time to watch "the great dust settle and the great silence move down upon their world (page 107, online)" after the city and everyone in it was destroyed by a nuclear bomb. On the bright side, Montag finds a group in the woods who also escaped the city in order to change the world with their knowledge. Montag finally finds his purpose, and knows that he will eventually change the world for the better.