Final answer:
The old woman's decision to set fire to herself and her home along with her books causes Montag to feel guilty and creates a turning point in his perspective on book burning.
Step-by-step explanation:
At the next fire, the old woman causes it to be different than most of the alarms that Montag and the other firemen respond to by choosing not to leave her house and instead setting it and herself on fire along with her hidden books. Montag feels guilty and inconvenienced because he begins to question the morality of his actions and the value of the books they are burning. The woman's resolve and ultimate self-immolation with her books profoundly impact him, and he starts to see the fires and his role in them differently. This event eventually leads Montag to steal a book and seek a deeper understanding of why the society chooses to burn them.