It is early February. Seth has been to see Dinah at Snowfield, and she has again rejected his offer of marriage. Hetty and Adam are preparing for a March wedding and everything seems fine, though Hetty is sometimes subject to strange fits of depression. We soon find out why: Hetty is pregnant and close to despair. She contemplates suicide but is afraid to go through with it and finally decides to run away to Arthur, who is stationed in Windsor, in the south of England. She tells Adam that she has decided to visit Dinah for a week and thus gets away without arousing suspicion.
The hint of sympathy in the characterization of Hetty expands at this point in the novel until the reader, who has been inclined to condemn the girl before, finally finds himself "on her side." It is a rather surprising switch; one gets the impression that Eliot's attitude toward her own character had changed. Gone are the constant references to Hetty's vanity and selfishness; she is now "a foolish lost lamb" and a "young, childish, ignorant soul." Partially through metaphors like these, the characterization changes from almost completely negative to something much closer to that ambiguity which Eliot said she aimed at in her writing (see the Analysis on Chapter 29). Those thoughts and actions which earlier were ascribed to Hetty's shallowness of spirit are now treated as the result of her naivete. No longer a "bad girl," Hetty has become a helpless victim, a victim of her own weakness and of Arthur.
As is typical of Hetty, she never considers admitting her pregnancy; she is, as we know, greatly influenced by the desire for other people's approval, and this course of action seems like the worst possible alternative to her. This lack of openness is one of the causes of Hetty's tragedy; pride prevents her from seeking the help she needs. Thus, Eliot would say, do the consequences of a bad action operate. Because Hetty has given herself to Arthur, she is pregnant. Because she has done something which the people around her consider shameful, she cannot admit the fact. Thus she is doomed to wander alone; her thoughtless behavior has influenced her in such a way that she is cut off from contact with the rest of the human race. She is trapped by her own act, an act which accurate foresight would have prevented her from committing.
Going to Arthur seems to be her only means of escape. She knows now that he doesn't love her, but that no longer makes much difference. She feels that he "would receive her tenderly — that he would care for her and think for her," and at this point protection is what Hetty seeks above all. She cannot face the scorn of the people at home. Arthur will not make her a great lady, but at least he can offer her basic security.
With the exception of Chapter 32, which contributes nothing at all to the plot, Book IV is concerned with the novel's central conflict and the first consequences of Hetty and Arthur's rash affair. It accomplishes two purposes. The lovers' triangle takes its final form as Adam defeats Arthur in a fight, drives him away from Hetty, and becomes engaged to her himself. The three lives become inextricably intertwined. It also sets the stage for the tragedy which will follow in Book V. As this section ends, Adam, Arthur, and Hetty are separated and each is living in his own world. Adam thinks Hetty is going to marry him, Arthur thinks the affair has ended safely and feels secure, while Hetty is wandering lost and helpless, the only one of the three in full possession of the truth. Hetty's pregnancy is slowly and inevitably bringing the plot to a climax. Eliot ends Book IV at a point where everyone's happiness is threatened; it is only a matter of time. The consequences slowly unfold; Adam, Arthur, and Hetty are trapped in a maze of circumstances, deriving from Arthur and Hetty's relationship, from which there is no escape.