Humbert divorces and moves to the United States where he edits perfume ads and continues work on his "comparative history of French literature for English-speaking students" (1.9.1).
He has a breakdown and goes to a sanatorium for more than a year, returns to work, re-enters the sanatorium.
He participates in an exploratory voyage to the Arctic, during which he is supposed to make observations about the psychological state of his colleagues. He doesn't enjoy the job because "Nymphets do not occur in polar regions" (1.9.3).
Upon his return, Humbert suffers another breakdown and enters the sanatorium a third time. Mocking the psychoanalysts helps pass the time though, as he loves outsmarting and misleading them about the causes and symptoms of his disorder. He is particularly amused that they think he is "potentially homosexual" (1.9.5).