Vladimir Nabokov wrote Lolita to attempt to show a perspective from a psychologically deranged individual who is, in essence, in love with his twelve year-old stepdaughter, Lolita. The story goes from bad to worse as time progresses and as the main character and author Humbert spends more time with Lolita. After the death of his wife, Charlotte, we see his psychological sickness progress. Ultimately, Lolita shows that Humbert is indeed performing bad things, but through Nabokov's character depth of Humbert, we sympathize with him not because he is bad, but because he is sick. There are two main drives that ignite this story, obsession and denial.
Humbert lives his life for necessity. What he needs or wants at that particular moment is what drives him. Possibly affected by Annabel's death at the early stages of his life, he becomes obsessed with Lolita. He wants and needs Lolita, and that is his only desire. He manipulates Charlotte into thinking he loves her, and he uses this as an excuse to be around Lolita constantly. Lolita fools with him, she teases him and this only ignites his desire more. Humbert does all he can to thwart Lolita's plans of being with boys and getting out to have her own life. His jealousy and paranoia keep Lolita from maintaining a normal life. He is unaware, though, that one with the same desire and passion as he is on their trail, in the form of Clare Quilty. When Lolita eventually disappears, his drive is to find Lolita by retracing every portion of the long journey that he and Lolita shared, while reducing his sexual tension with Rita, the disturbed woman he has an affair with while searching for Lolita. As he hears what had happened, his necessity becomes the desire to find Quilty and to harm him. He does so by killing him. As the end of the story closes, Humbert reveals that he is in jail awaiting trial for the murder of Quilty. His drive at that point is to free himself of the charges brought against him.