The night Miss Maudie's house burns down, Atticus wakes up Jem and Scout and leads them outside, both in case the fire spreads and because the neighborhood is gathering to try to help, saving what they can from Miss Maudie's during the emergency.
Instructed by Atticus to stay out of the way, Scout and Jem watch the frightening event, and the confusion is so great that it isn't until later, when Atticus questions her, that Scout realizes someone placed a blanket around her shoulders during the commotion:
As we drank our cocoa I noticed Atticus looking at me, first with curiosity, then with sternness. "I thought I told you and Jem to stay put," he said.
"Why, we did. We stayed—"
"Then whose blanket is that?"
"Yes, ma'am, blanket. It isn't ours."
...I turned to Jem for an answer, but Jem was even more bewildered than I. He said he didn't know how it got there, we did exactly as Atticus had told us, we stood down by the Radley gate...Jem stopped.
"Mr. Nathan was at the fire," he babbled, "I saw him, I saw him, he was tuggin' that mattress—Atticus, I swear..."
"That's all right, son." Atticus grinned slowly. "Looks like all of Maycomb was out tonight...We'd better keep this and the blanket to ourselves. Someday, maybe, Scout can thank him for covering her up."
"Thank who?" I asked.
"Boo Radley. You were so busy looking at the fire you didn't know it when he put the blanket around you."
Though she did not realize what was happening at the time, this interaction Scout has with Boo Radley is very important. It illustrates to her the difference between the reclusive figure she has conjured up in her mind and the real Boo, who was concerned enough for Miss Maudie to come out of his house and concerned enough for Scout and Jem to make sure they stayed warm. His kind gesture conflicts with the unfounded fear Scout feels regarding Boo. This incident is a crucial aspect of the lessons Scout learns throughout the novel about community, the good in people, and the dangers of judging others without knowing their stories.