The book has several subtle hints to what causes the change. First of all, I think that Clarisse, the sixteen-year-old girl (going on seventeen), influenced Montag a lot. After they met, they became really good friends, and they began to talk seriously to each other, and not just talk playfully. Clarisse continued to tell Montag things the way she saw them, and she talked to him a lot about things her uncle told her. She always told him about how her uncle kept telling her how firemen were in the many years before, and how they would put out fires, rather than make them. When Montag was informed that Clarisse was hit by a car and killed, he got really depressed, and everything that Clarisse had ever told him, or done with him, stayed with him, and he never forgot it. After her death, the things that Clarisse told Montag influenced him more and he really paid attention to what she had been telling him all along. I think that Clarisse had the, over all, biggest impression an Montag, making him have a different perspective and look at things differently.
Not too long after Montag learned about Clarisse's death, he received a call about a house that was found which had several books kept in it. He was told that an old woman owned the house. Montag Went to the house, and while he was there, the lady set herself