At the Endicott Family Hotel, Charles asks after Sarah and is told by Mrs. Endicott that she has fallen down some stairs and twisted her ankle badly. He goes to visit her in her room, and she begins to cry. Charles is overwhelmed by lust for Sarah. They look into each other's eyes for what seems "an eternity" and then Charles pulls Sarah toward him and covers her in kisses (273). After saying "we must not," Charles undresses and penetrates Sarah (273). He ejaculates immediately.
A mixture of guilt and “horror” hits Charles after he has sex with Sarah, and his thoughts turn to Ernestina and her father (275). He apologizes to Sarah, and says that he must break off his engagement with Ernestina in order to marry Sarah. Sarah says that she has been wicked by taking him away from Ernestina, and that she doesn't ask for anything more from him - they should go their separate ways and pretend that nothing has happened. She says she loves him. Charles notices some blood on his shirt, and realizes that Sarah was actually a virgin. She has lied about having had sex with Varguennes, and Charles suspects that her motive for lying was to be able to blackmail him and have him in her power. Charles wants to know why she lied to him, but Sarah "cannot explain" (279). Sarah tells him that he will never be able to be happy with her, and that he cannot marry her. Bewildered and frustrated, Charles leaves her room abruptly.
After leaving the Endicott Family Hotel, Charles goes into a church and prays. However hard he tries, he cannot believe that there is a God hearing his prayer; he also keeps seeing Sarah's face on the statue of Christ crucified. Charles discusses his situation with himself and with Christ; he tries to take the moral high ground by claiming he was deceived by Sarah and must return to Ernestina and fulfill his engagement promise, but Christ and his better self argue that Charles is hiding behind his "duty" and is neglecting what is really important. The realization that he doesn't have to care what everyone else thinks about him, because they cannot judge him properly, leads Charles to imagine what it would be like to marry and live with Sarah. Charles kneels down to pray again, and then leaves the church.
Charles returns the keys of the church to the young pastor from whom he borrowed them, and returns to his hotel. He eats dinner and begins to write a letter to Sarah. He claims that he loves her deeply, and that he intends to break off his engagement with Ernestina in order to marry Sarah. Charles instructs Sam to take the letter to the Endicott Family Hotel and wait for a reply; Sam returns without a response from Sarah. Charles and Sam go back to Lyme, and Sam tells Mary what is happening, taking care to reassure that he loves her and would rather leave Charles' service than lose her.
Ernestina greets Charles at Aunt Tranter's house when he arrives in Lyme Regis. He tells her that he isn't worthy of her, and that he must break off their engagement. Ernestina initially thinks he must be joking, but realizes that he is serious. Charles explains that he entered into the engagement for selfish reasons - he felt his life was purposeless, and he was attracted by Ernestina's large dowry and future inheritance. Ernestina tearfully begs him to reconsider, and promises to do anything he wants if only he will stay with her. She also accuses him of lying about his motive for breaking off the marriage plans. Charles admits that there is another woman, one he has known for many years, and who has recently come back into his life. Furious, Ernestina threatens to blacken his name and tell the world of his dishonorable behavior; she faints and Charles summons Mary to take care of her.
The tension between Sarah and Charles comes to a head in this chapter - it has been building throughout the whole novel, and now finally the two characters consummate their strange relationship. Charles is very much the agent in this scene, and Sarah is passive. Just as it is Charles who seeks Sarah out at her hotel, so it is also Charles who makes all of the sexual advances in this chapter; Sarah is "passive yet acquiescent" (274). Sarah's emotions in this scene are muted - her tears before she and Charles kiss are very subtle and hardly visible, and she is very quiet and inexpressive during intercourse, compared to Charles' "hunger" and "frustration" and lust (274).
We might also note that this lovemaking scene doesn't play out quite how we might expect. Charles and Sarah are the main characters of the novel, and have been pulled together by fate into a strange meeting of souls that the reader hopes can blossom into a passionate love. We would expect, then, that this first love scene, the consummation of their relationship thus far, would be outstanding in some way - very passionate, or very tender, and hugely moving and significant either way. But Charles climaxes after "ninety seconds" - the scene can't exactly be called an unmitigated success. The narrator almost seems to be making fun of Charles; we pity him, though, because his frustration is due to Victorian denial of sexuality.
The imagery used to describe Charles' feelings after having sex with Sarah is military and negative. He is compared to a city that has been hit by an "atom bomb," and to the last man alive after the explosion, slowly being poisoned by radioactive feelings of guilt (275). The enormity of what has just happened - even though it was only a few seconds of penetration - is not lost on Charles, who understands how unacceptable his behavior is to society and to his fiancée and her father. Charles' guilt causes him to feel paranoid: he automatically assumes that the footsteps he hears outside the window are those of a police officer, representing "The Law" (275). It is ironic that Charles has entered the Endicott Family Hotel pretending to be "a gentleman of the law," and now he feels so guilty that he feels he should be judged and punished (270).
Because we know much less about Sarah than we do about Charles - the narration has spent little time in her mind, and much in his; Sarah is a much more mysterious character than Charles is - the news that Sarah is a virgin comes as just as much of a shock to the reader as it does to Charles. We learn something new about her, but there are still a "swarm of mysteries" surrounding her (278). As Charles asks himself, "Why? Why? Why?" (278). It is as if we take a step closer to understanding Sarah, and realize that there is much more that we cannot understand about there.
Charles experiences an internal battle between reason and emotion in this chapter, brought on by the conflict between his reason and faith in science, and his desire to have a God to speak to and forgive him his sins. Poor Charles "weep[s]" for "his inability to speak to God," even though he knows that he "is right to do without [Christianity's] dogma" (282). This internal tension results in a silent and extended discussion "between his better and his worse self" which morphs into a discussion between him and Christ (282). The outcome of the conversation is that Charles realizes that he is simply taking the easy route by constantly referring to his "duty" to Ernestina and to society, and he is being a coward by not following his heart and loving Sarah. Sarah represents freedom, the ability to defy society and not care what others think of him, and Charles by the end of this chapter is ready to embrace that freedom.
Charles' letter is touching, full of endearments like "dearest" and "sweet," and it is clearly intended to be a love letter in which he declares his "honorable" intentions toward Sarah and his intention to leave Ernestina for her (290). He writes several drafts of this letter, which shows his less spontaneous side. After having been so rash toward Sarah in terms of making love to her suddenly and without preamble, Charles is determined to do everything correctly. Even when he thinks he is casting off the shackles of duty in order to live the life he wants, he has to make sure that he is acting decently and with propriety - it is a fundamental part of his character. This is the reason why he isn't able to make his letter satisfactorily tender; he cannot chase out the "formality" from his way of addressing Sarah (290). Charles is a product of his environment, and his gentleman's instincts are so firmly rooted in him that the reader might wonder if he will be able to fully disengage himself from societal expectations and live with Sarah.
There are fascinating parallels between Charles as he breaks off his engagement with Ernestina, and Sarah in the scene immediately after she loses her virginity to Charles. Both of them claim to be unworthy of their significant others - Sarah states simply that she is not worthy of Charles, and doesn't expect him to leave Ernestina for her because Sarah has been wickedly calculating this encounter and hoping that they would have sex. Charles also claims to be unworthy of Ernestina, due to calculations - he says that he was just marrying her for her money. The second parallel is that both Sarah and Charles are not completely honest during their conversations. Sarah is honest when she is forced to tell the truth about what happened with the French lieutenant, but she continues to conceal her motives. Charles invents a story about how he was attracted to Ernestina because of her father's fortune - both are deceiving in some way, by omission or by "half-truths" (298). Even when Charles decides to tell Ernestina that there is another woman, he conceals her name, and lies by saying he has known her for many years.
Ernestina reveals a depth of character in this scene that we have not seen before. She is self-aware, explaining in a few sentences all the worst things about herself, that we have witnessed over the course of the novel. She also loved Charles more than we saw from her diary entries and interior monologues; she truly respects him and wishes that he had more "[f]aith in himself" (297). The fact that Ernestina blossoms - or at least shows her potential to blossom into a good person - at this point in the novel, where Charles must make a crucial choice between her and Sarah, makes his decision all the more difficult.