Raskolnikov is deeply offended by Luzhin's offer of marriage because he views Dunya as sacrificing herself to benefit him, and he cannot stand the idea of someone making such a sacrifice for him.
He makes a comparison between his sister's sacrifice to help her family and Sonya's sacrifice to help her family. He wonders if Dunya's marriage to Luzhin is not also a type of prostitution and may even be worse because Sonya's was for necessity and Dunya's could be for convenience.
The parallel between the two sacrifices troubles Raskolnikov because he can do nothing about them. This brings about the reoccurrence of the "Do you understand, sir, do you understand what it means when you have absolutely no where to turn?" theme. This parallel deeply troubles him because his present situation is also desperate and hopeless. He feels strongly that Dunya is sacrificing herself, but he can do nothing to alleviate the situation or prevent it.
Raskolnikov is deeply disturbed when he encounters the young girl, who has been abused and who is being followed by a man with evil designs upon her. This scene prompts the humanitarian side of his character into performing an act of protection. In his attempt to protect the girl, Raskolnikov calls the man a "Svidrigailov," thus making this name into the embodiment of depraved sensuality.
Raskolnikov's humanistic and compassionate nature is further revealed in his attempts to protect the young girl. He gives her almost all of his scarce money in order to send for a cab. The question arises: Would he have been so protective of the young girl if he had not just received the letter from his mother? Immediately after trying to help the young girl, he suddenly reverses himself and says "let them be." That is, suddenly, the cold, intellectual Ubermensch aspect of his personality takes over, and Raskolnikov maintains that such trivial happenings do not concern him — that he is too far above or removed to be involved. Carried further, he also should not be concerned with what happens to Dunya or Sonya, that is, if he is the true Ubermensch.
At the end, Raskolnikov's unexpected desire to see Razumihkin, his logical and rational friend, is caused by his awful feeling that he has "no where to turn."
