I think there's a bit of a deeper meaning to the end of Chapter 35. As we see when Humbert goes downstairs after killing Quilty, there appears to be a party, or at least some sort of social gathering, occurring, none of which Humbert noticed before, dismissing the noise they had been making as "a mere singing in [his] ears." The people at this gathering seem not to care about the fact that he has just committed murder upstairs, and one even congratulates him: "Somebody ought to have done it long ago." I, for one, am brought to question how many, if any, of these people are actually present, or whether they are a metaphor meant to convey the fact that Humbert is going insane, and is actually imagining what is going on around him. After all, he did just kill someone quite gruesomely.