From the wild, frantic scene in Chapter 2, we move to a quieter but more intense chapter where we see Luzhin's attempt to frame Sonya. His elaborate preparations to prove her to be a thief indicate his desperation, his vileness, and his amoral stance. His attempt to disgrace her is only so as to cast aspersion upon Raskolnikov, thereby hoping to prove to Dunya that he was right in his judgment about Raskolnikov's relationship to Sonya. He is ultimately the most despicable person in the novel, and this scene proves that Raskolnikov was right in strongly opposing Dunya's marriage to him.
Sonya leaves before the horror of the scene is over. When she goes to her own room to escape Katerina's hysteria, Amalia Ivanovna's anger, and the general air of disillusionment, she intuitively knows that Raskolnikov will follow her. Note that Raskolnikov watches Sonya's behavior and concludes that "she was capable of bearing everything. . .with patience and serenity."
