Lee presents Boo's character in an evolving way through the eyes of the children.
Boo Radley is first introduced through the children’s games and the stories they tell. He is a monster and an unknown entity at first. Then later he becomes are more developed character as we start to see him as not disturbed and violent, but shy and calm.
When we are first introduced to Boo Radley, he is a monster. The children learn about him from neighborhood gossip, and they are afraid to go by his house. The nuts from their tree :lay untouched by the children” in the school (ch 1).
Jem gave a reasonable description of Boo: Boo was about six-and-a-half feet tall, judging from his tracks; he dined on raw squirrels and any cats he could catch, that's why his hands were bloodstained-if you ate an animal .raw, you could never wash the blood off. There was a long jagged sear that ran across his face; what teeth he had were yellow and rotten; his eyes popped, and he drooled most of the time. (ch 1)
Clearly, this is not an accurate description. Boo has become a phantom, and a childhood joke. Yet, the children are still very curious about him and continue to imitate him in their game. When Scout finds a piece of gum in the Radley tree, she is hesitant to eat it when she realizes it came from the Radley’s, but she brings it home.
I ran home, and on our front porch I examined my loot. The gum looked fresh. I sniffed it and it smelled all right. I licked it and waited for a while. When I did not die I crammed it into my mouth: Wrigley's Double-Mint. (ch 4)
This is the first of many gifts from Boo, but one of the most remarkable is the little carved dolls that show he has watched the children. When Boo’s father plugs the hole so Boo can no longer give them gifts, it shows that Boo is still being victimized.
Then another amazing thing happens on the day of Miss Maudie’s fire, when Scout and Jem realize that Boo has come out and placed a blanket on Scout while she was not looking.
My stomach turned to water and I nearly threw up when Jem held out the blanket and crept toward me. "He sneaked out of the house - turn 'round - sneaked up, an' went like this!" (ch 8)
Scout’s reaction is fear, but Jem realizes that Boo has done a generous thing and doesn’t want anyone to find out because Boo might get in trouble. Boo does another generous thing for him when he mends the pants Jem leaves behind when sneaking onto the Radley porch.
By the end of the book, the children view Boo as a benevolent and shy figure of childlike innocence. "In the wake of the trial and their confusion over its injustice, they are shown a parallel in their own unwarranted treatment of Boo Radley, who turns out to be their protector" (enotes character analysis, Boo Radley). After Boo saves Jem, Scout walks him home in the most polite of ways. At the end of the story, Scout "remembers the past and realizes that they have in effect been Boo’s children through time" (enotes summary, ch 31).