Devastated by his mother's death, and imagining himself responsible, Clym falls into a long period of illness and depression. Eustacia, who has kept secret her role in Mrs. Yeobright's death, feels unhappier than ever, and increasingly takes solace in Damon Wildeve's company. When Clym recovers from his histrionics, he slowly reconstructs the events leading to his mother's death. From Christian Cantle and Diggory Venn he learns that his mother had planned to visit him. From Johnny Nonsuch, the boy to whom Mrs. Yeobright delivered her last words, Clym finally learns the truth. Johnny saw a man--who Clym rightly suspects was Damon Wildeve--enter the house; he saw Mrs. Yeobright knock and Eustacia look out the window but not open the door; and he saw Mrs. Yeobright walk away, dejected. The normally patient Clym becomes furious. He blames Eustacia for his mother's death; she explains the nature of the confusion, but will not tell which man visited her on that day. After their fight, she leaves the house, moving back to Mistover Knapp with her grandfather. There, she is cared for by Charley, the servant who has come to love her; when she contemplates suicide, he locks away the pistols in the house.
In his attempt to entertain Eustacia, Charley makes a bonfire on the anniversary of the fateful day on which the narrative started, November 5th. Seeing the fire--which Charley, of course, had not intended as a beacon--Damon responds to the old lover's signal by visiting Eustacia. Once again she bemoans her fate, and he professes his love. They plan for him to help her escape to Paris, although it is not resolved whether or not he will join her. Meanwhile, Clym has gone to visit Thomasin. They discuss Clym's predicament--he is still in love with his estranged wife--and Clym writes Eustacia a letter asking for a reconciliation. When Damon returns, Thomasin, vaguely suspecting that something is afoot between Eustacia and him, asks him where he goes on the heath at night, and he becomes angry.
The next day, November 6th, Eustacia sends Damon the appointed signal: they are to leave that night. The letter from Clym arrives at about 10 PM, but it is not given to Eustacia. At midnight, Captain Vye notices that Eustacia is not in the house. She has slipped out the door with her things, and she is headed towards the Quiet Woman Inn, to meet with Damon. Eustacia's inner torment is no less violent than the stormy weather: she realizes that she has no money, and that she will need to take Damon with her to Paris, to provide for her. But she also bemoans the fact that Damon is not ambitious or grand enough for her. In a cottage nearby, the superstitious Susan Nonsuch is busy working a countercharm against Eustacia's supposed witchcraft. Nonsuch fashions a wax doll likeness of Eustacia, and, filling it full of pins, melts it in the fire. The sense of foreboding is indisputable.
Sitting alone at home and waiting for a response to the letter he sent to Eustacia, Clym is visited by Thomasin, who tells him that Damon Wildeve is to run away with Eustacia. Captain Vye, too, visits, and tells Clym that Eustacia has vanished. Frightened and concerned, Clym goes out on the heath, despite the storm, to find Eustacia. Thomasin, after a delay, follows him, bringing her infant daughter. She loses her way on the darkened heath, and is lucky to stumble upon Diggory Venn, who joins her in her search. Together, they head towards the Quiet Woman inn. The action soon comes to a climax. Clym encounters Damon Wildeve, who is prepared to meet Eustacia and flee the heath. They hear the sound of somebody falling into the nearby weir, (an artificial pool formed by a dam). They dive into the whirlpooling weir, in an attempt to save Eustacia. Diggory Venn soon arrives on the scene and, sending Thomasin for help, attempts a rescue of his own: he pulls Damon and Clym out of the water, and later, with the help of the locals, finds Eustacia's body. It is discovered that Damon and Eustacia are dead, but that Clym will recover: as is characteristic, he blames himself for all the deaths.
This is a slow-moving novel: it is not unusual for Hardy to spend an entire chapter discoursing on the personalities of his main characters. But this "book," "The Discovery," is characterized by quick movement and dramatic--even melodramatic--situations. In a novel in which events take months to unfold, the greater part of the crucial action takes place within the space of a few days, and is packed into a few small chapters. Indeed, Hardy's narrative art seems better suited to lengthy exposition than to action and drama: these are also, arguably, the weakest chapters in the novel. In contrast to the lyrical stillness of Hardy's descriptions of the heath, here we encounter a prose-style veering toward the overwrought. Note the dialogue in this section, which, while often overly ornate throughout the novel, here seems to evade Hardy's control entirely. Listen to the raving Clym, emoting with all the histrionics of a soap-opera hopeful: "If there is any justice in God let Him kill me now. He had nearly blinded me, but that is not enough. If He would only strike me with more pain I would believe in him forever!" At the same time, it should be borne in mind that Hardy has a purpose to his melodramatic writing style. The characters--especially Clym, who throughout has been a model of stoicism and deliberation--lose their senses of proportion and perspective in this section: note Clym's anger, Thomasin's bizarre decision to bring her infant child on her walk through the storm, Eustacia and Damon's desperate plot. Thus perhaps it is only fitting that the prose, in its intemperate passion, imitate the wildness of the characters.
This section is also atypical of the rest of the novel in its failure to reveal a crucial detail: did Eustacia jump into the weir, or was her death an accident? This lack of information is all the more remarkable in a novel otherwise so careful in revealing psychological truth. We know that Eustacia had contemplated suicide earlier, leading Charley to hide Captain Vye's pistols in order to ensure her safety. And we know that Eustacia, in her despair while walking across the heath to meet Damon, was conceivably suicidal. "There is something grievous the matter," the narrator informs us; and her "Can I go, can I go?" may be taken as a reference either to her voyage to Paris or to her suicide. This reluctance to reveal the truth of what occurred may be taken as another instance of the narrator's unreliability, his refusal to play the role of authority, even within his own narrative. It may also be a clever narrative move designed to more fully realize the characters in the mind of the reader. The reader does not know whether or not Eustacia committed suicide; thus, the reader is forced to extrapolate based on his or her prior knowledge of Eustacia. The character assumes a reality of her own; her actions are based on her own personality rather than the decrees of a narrator.