In Chapter 14 of Harper Lee’s novel To Kill a Mockingbird, Scout feels that her older brother, Jem, has broken the “code of [their] childhood” by behaving like an adult. Jem has informed their father, Atticus Finch, that their young friend Dill has run away from home and is hiding underneath Scout’s bed. By doing so (Scout thinks) he had broken “the remaining code of our childhood.”
Earlier in the same chapter, however, Jem had also begun to act like an adult. He had said to Scout,
“you can’t hold something in your mind but a little while . . . . It’s different with grown folks, we—”
To make matters even worse (at least from Scout’s perspective), a few moments later Jem had also threatened to “spank” Scout – a threat that provoked her to attack him physically:
“Ain’t so high and mighty now, are you!” I screamed, sailing in again. He was still on the bed and I couldn’t get a firm stance, so I threw myself at him as hard as I could, hitting, pulling, pinching, gouging. What had begun as a fist-fight became a brawl. We were still struggling when Atticus separated us.
As both of these episodes show, Jem has begun to think of himself as a grown-up. He has begun to feel older and superior to Scout and Dill, and in Jem’s eyes he has thus violated “the remaining code of our childhood.” Since the entire novel is about the process of maturation for both Scout and Jem, these moments when Scout feels estranged from (and even betrayed by) the maturing Jem are especially significant.