As the story unfolds the book becomes far more the account of the mental state of Jacky S. than a study of Lilian and her depravity. One of the most exciting incidents, in its effect on the narrator, is one in which he has no direct part. Lilian describes a young law student's vigorous attempt to rape her. Jacky is neither jealous nor outraged. To hear of the young man's assault on the girl he himself loves acts as a powerful aphrodisiac - to use his own term - and he makes her repeat it to him often.

At this time the hero's emotions of jealousy begin their pathological development. He presents Lilian with a copy of Sade's Justine, urging her to pay particular attention to Saint Fond's account of the pleasure to be derived by seeing one's mistress in the arms of another man. In a little while Jacky even encourages Lilian to try and excite her step-father, Eric Arvel, the very source of the jealousy, which is to torment him later in the book.

"You should rub against him whenever you call," says Jacky to the girl, "and let your cheek and hair touch his face while type-writing together, etc., and then look at his trousers and see if he is in erection."