In Lolita, Nabokov likes to use dialogue based on information as yet unavailable to the reader, like the two pages of dialogue in Chapter 27, beginning,"We should be in Briceland..." What Lolita was too embarrassed to confess?
In Chapter 27 of Part One of Nabokov's novel, Lolita tells Humbert about some of her activities at the camp. Finally he asks, "C'est bien tout?" ("Is that everything?") And she replies:
"C'est. Except for one little thing, something I simply can't tell you without blushing all over."
Later in Chapter 27, when Humbert is putting her to bed in their hotel room in the bed he intends to share with her after she is sound asleep, Lolita gives two more hints:
"If I tell you--if I tell you, will you promise [sleepy, so sleepy--head lolling, eyes going out], promise you won't make complaints?"
"Oh, I've been such a disgusting girl," she went on, shaking her hair, removing with slow fingers a velvet hair ribbon. "Lemme tell you--"
"Tomorrow, Lo. Go to bed, go to bed--for goodness sake, to bed."
What that one thing was does not come out until Chapter 32 of Part One, after she and Humbert have made love at The Enchanted Hunters. Instead of having Lolita describe her delinquency in her own dialogue, Nabokov simply has Humbert give a synopsis.
At first, Lo had refused "to try what it was like," but curiosity and camaraderie prevailed, and soon she and Barbara were doing it by turns with the silent, coarse and surly but indefatigable Charlie [Holmes], who had as much sex appeal as a raw carrot but sported a fascinating collection of ccntraceptives which he used to fish out of a third nearby lake...
It would seem that Humbert is trying to excuse his own conduct by explaining that he did not, after all, violate a young virgin. At the very end of Chapter 31, he says:
Did I deprive her of her flower? Sensitive gentlewomen of the jury, I was not even her first lover.
It is hard to read Lolita without getting the extremely strong impression that Vladimir Nabokov is writing about his own fantasies. He disclaims being a nympholept in a note appended to the novel, but he definitely seems to have been preoccupied with the subject for many years. There are similar themes in Invitation to a Beheading (1959) and Laughter in the Dark (1938). He also published a novelette titled The Enchanter (1939; in English translation 1986), which had essentially the same premise as Lolita. A man marries an unattractive middleaged woman in order to get close to her teenage daughter with whom he is obsessed, and the girl's mother conveniently dies, leaving the stepfather the girl's legal guardian.
In other words, it would seem that Nabokov wanted to mitigate the many crimes committed by his hero, or alter-ego--including that of violating the Federal Mann Act by transporting the girl across countless state lines across America for immoral purposes--by carefully establishing that at least he was not raping a virgin minor.