As the novel opens, the wild landscape of Edgon Heath broods alone, save for an old man walking home. The old man, Captain Vye, passes a reddleman, Diggory Venn. Diggory is discreetly transporting a distressed young woman. She is Thomasin Yeobright, humiliated that her wedding to Damon Wildeve was halted due to an issue with the marriage licence in a nearby community.
The truth is more complicated, though. Wildeve is still infatuated with his former partner, the passionate and mysterious Eustacia Vye, who lives on the heath by circumstance but wants nothing more than to escape it. She lights a bonfire that evening to draw him to her. The fire attracts only minimal attention, since there are bonfires all along the heath to commemorate November 5th. Wildeve correctly interprets her signal, and meets her. When Diggory learns of their liaison, he plans to intervene on Thomasin’s behalf. He has long loved her, and though she once rejected his proposal because of his lower status, he is dedicated to ensuring her happiness, even with another man.
Just as Eustacia’s affection for Wildeve begins to wane, an exciting prospect returns to Egdon. Clym Yeobright is a local man who has made his way in the world as a diamond merchant in Paris. His visit prompts Eustacia to facilitate a meeting between them, which eventually results in a mutual attraction. Eustacia makes her disinterest known to Wildeve, and he finally marries Thomasin.
She is disappointed, however, to discover that Clym has rejected his cosmopolitan lifestyle in hopes of founding a school on the heath. Hopeful that she can change his mind, Eustacia agrees to marry him. Clym’s mother, Mrs. Yeobright, disapproves of both Thomasin's and Clym's weddings, and is further irked that her son Clym would refuse to exploit his intelligence and talent away from the heath. She refuses to attend his wedding.
Clym's studies in schoolkeeping are so intense that his eyesight fails, and he is forced to take a job as a furze cutter to generate an income. Eustacia is further disappointed in Clym's choice of a low career, and realizes she might never escape the heath. Her feelings for Wildeve are reawakened, however, when she learns that he has inherited a fortune, and plans to travel the world.
Wildeve visits the Yeobright house one day, but Clym is asleep. Eustacia is shaken by his visit, and then confused when Mrs. Yeobrght suddenly arrives on her own unannounced visit. Eustacia ignores her knocks, and, believing she has been spurned by her son, Mrs. Yeobright attempts the long journey back to her home, but passes out and dies on the heath from a snakebite.
Clym holds first himself, then Eustacia, responsible for Mrs. Yeobright’s death. Spurned by his grief and hatred, Eustacia returns to her grandfather’s house, and Wildeve agrees to help her escape Egdon. She sets an evening for her escape, and does not cancel the plan even when that evening proves to be impossibly stormy. That night, Thomasin, Diggory, Clym and Captain Vye search for the missing couple, but discover only tragedy after Eustacia seems to drown herself and Wildeve dies in the rescue attempt. Clym, too, is wounded in his rescue attempt, but survives.
Thomasin initially moves in with Clym and her daughter after the tragedy. Diggory Venn returns as a wealthy and dependable farmer, and she agrees to marry him. Clym never transcends his guilt and shame, and eventually turns to preaching to fill his solitude.
