Why did the people of Molching hold a bondfire? Why were they burning books?

The bonfire is part of the celebrations for Hitler's birthday. Propaganda, banned and censored books, and written material from the era between World War I to the rise of the Nazis are collected and burned. The Speaker starts talking about Communism and Liesel revisits her dark past. She sees a girl in pigtails staring at the fire which reminds Liesel of herself.