Death emphasizes the danger of the situation in the Hubermann household now. Max sleeps in Liesel's room, in the empty bed once intended for Werner. The next day the Hubermanns keep Liesel home from school, and Hans leads her to the basement, where he tells her the story of Erik Vandenburg, and explains who Max is, and reminds Liesel of her promise the night of the book-burning. He insists she must keep Max a secret from everyone.
From the start Max symbolically replaces Werner as Liesel's brother-figure. Again Hans must make Liesel understand the broader implication of her actions. In such a situation she has to grow up fast – a childish mistake could lead to all of them being arrested. The sense of danger is very high now.
Hans lists what will happen if Liesel mentions Max to anyone, and he tries to be harsh to make sure she understands: Hans will burn Liesel's books and then he and Rosa will be taken away forever. Liesel cries, but she understands the gravity of the situation.
Just like on the night he slapped her, Hans must be cruel for Liesel's own good. It is telling that part of the potential horrible punishment is burning her books – Liesel's most precious possessions.