Breaking Dawn begins with another preface in which our narrator, Bella, once again faced with death. This time, though, it's a person she loves who's about to kill her. She decides that her love for that person leaves her no choice but to sacrifice her life.
Cut to: Bella driving her new Mercedes Guardian, an engagement present from Edward. She feels uncomfortable because everyone in town is staring at her. As she passes by "Missing" posters of Jacob, we learn that he disappeared after receiving her wedding announcement.
Bella recalls Charlie's reaction when she told him her decision to marry Edward. At first, he assumed she was pregnant. Later, both he and Renée admit that they knew it was coming. Bella and Edward tell them that after their honeymoon, they'll attend college at Dartmouth.
Bella reminds Edward that he promised to make love to her after their wedding. Edward expresses his sadness over the fact that she'll never be able to get pregnant with his child.
While Edward is out on a bachelor party hunt, Bella thinks about the mix of humans and vampires who will be at their wedding. The sisters from the Denali vampire clan are attending. She remembers Carlisle's story about their mother's death at the hands of the Volturi for creating an immortal child. The Volturi kill all immortal children in the vampire world, because their inability to control themselves threatens to expose the existence of vampires. The practice of transforming children into vampires is forbidden.
It's Bella's wedding day. Alice and Rosalie are getting Bella ready. Bella is nervous, but calms down when Charlie leads her down the aisle. Bella and Edward say "I do." Everyone congratulates the married couple, including members of the Quileute tribe.
Bella is surprised to see Jacob show up at the party. They dance together. Jacob teases Bella that she's not going on a "real" honeymoon. When he learns that she's planning to sleep with Edward, he loses his temper. Edward and Seth have to restrain him. His outburst causes Edward to second-guess his promise to Bella.
Edward and Bella spend their honeymoon on Isle Esme, an uninhabited island off the coast off Brazil. The island was a gift from Carlisle to Esme. Their first attempt at lovemaking leaves Bella with bruises and Edward with a guilty conscience, but she keeps pressing him, so they try again.
Days later, Bella realizes that she's pregnant and that her baby bump is growing at an unnatural rate. While she feels protective of whatever is growing inside her, Edward wants to get rid of "the thing." Bella secretly calls Rosalie for help. The newlyweds return home to Forks immediately.
The second part of the story is told from Jacob's point-of-view. He hears that Bella has returned from her honeymoon and that she's sick. Jacob believes that it's because she has become a vampire. He presses Sam and the werewolves to attack the Cullens for breaking the treaty. Sam resists, so Jacob goes to attack the Cullens on his own, with a special aim for Edward.
When Jacob sees Bella, he can tell that she's in great pain and is shocked to learn of her pregnancy. His initial rage at Edward subsides into confusion when Edward tells him of his plans to save Bella. The baby is killing her, but she won't let him abort it, and Rosalie acts as her bodyguard. Edward proposes an idea to Jacob that he give Bella what she wants in the form of a baby from Jacob. Jacob protests, but is intrigued by the idea, so he agrees to offer "his services" to Bella. Edward promises that if Bella dies, Jacob is free to kill him.
Bella politely rejects Jacob's offer. She plans on keeping her heart beating just long enough to give birth to her child and then to become a vampire. Confronted with Jacob's news, the werewolf pack decides that the unborn child poses un unknown threat, which needs to be destroyed, even if that means killing Bella to do so.
Enraged by Sam's decision, Jacob rises to the role he never wanted to have – that of the true alpha leader. He stands against Sam's orders and leaves the pack to protect Bella from them. Seth, who has become close friends with Edward, joins his side, followed by Leah, his sister.
Bella's condition is getting worse. On Jacob's spontaneous suggestion that the baby might crave blood, Bella starts drinking blood. The new diet not only makes her feel better, but it tastes good to her. Members of the pack appear to ask Jacob to come back, but to no avail. Against his will, Jacob's attitude toward the Cullen family softens.
The baby's accelerated growth causes Bella's bones to break, but Edward discovers that he can hear the baby's thoughts and that it loves Bella. Bella decides to name the baby Renesmee, if it's a girl. Edward is now taken with the baby too, and Jacob feels betrayed. He still believes the baby is a monster, slowly killing Bella. Desperate to get away from Bella's pull on him, Jacob tries to find a girl to imprint on, but has no luck.
Bella gives birth, but the baby breaks more of her bones and she loses massive amounts of blood. In order to save Bella's life, Edward changes her into a vampire. Jacob wants to kill the baby, but upon seeing the little girl's face, he imprints on her.
The third section of Breaking Dawn shifts back to Bella's perspective. The preface foreshadows Bella in a big fight, outnumbered by the Volturi.
The action picks up from Jacob's narration of Bella giving birth. She catches a quick glimpse of the baby before her life slips way. At the last minute, Edward plunges a syringe of venom in her heart and she undergoes the hellish pains of her transformation into a vampire.
Bella awakens to a new world. Her senses are sharpened, she's beautiful, and she's strong. As a newborn vampire, she should be blood-thirsty, so the Cullen family won't let her see her baby. Although she can feel the thirst for blood burning in her lungs, Bella's will power and self-control prove so strong that they eventually let her see baby Renesmee. The baby needs her, too. When Bella learns that Jacob imprinted on her baby, she snaps and attacks him, but is restrained by Edward and Seth.
Esme has renovated a cottage on the property for Bella and Edward to give them some privacy. They again make love, which Bella enjoys even more as a vampire. She misses Charlie, yet is lost as to how to break the news of her transformation to him. Jacob takes the matter into his own hands by first exposing himself as a werewolf to Charlie. He tells him that Bella has also undergone an "unusual" change but wants to have him in her life, if he can handle it. Bella manages to control her blood thirst when Charlie visits. He falls in love with his "special" grandchild.
In a matter of weeks, Renesmee can talk and grows big enough to walk – and hunt. When Bella and Jacob take her on a hunting trip, Irina, a sister of the Denali clan, misidentifies Renesmee as an "immortal child," which is one of the highest crimes under Volturi law. Alice sees Irina telling the Volturi this news and predicts that they will come and destroy the Cullens. Shortly after, she disappears with Jasper.
Bella receives a note from Alice that leads her to a man named J. Jenkins. She asks him to create fake travel identification for Jacob and Renesmee, so they can flee together, in case none of the Cullens survive the fight against the Volturi.
To stop the Volturi, the Cullens call in their friends to witness that Renesmee is not an immortal child, but is half-human. Training for a possible fight against the vastly superior Volturi army, Bella discovers that she can use the power of her "private mind" as a shield that can expand to protect others from the mental powers of even the fiercest Volturi.
Upon confronting the Cullens and their allies, the Volturi discover that Irina was wrong, and they immediately execute her. However, they remain undecided on whether to consider Renesmee as a threat to the vampire world's secret existence. Enter Alice and Jasper with a young man named Nahuel, another vampire-human crossbreed. He demonstrates that the crossbreeds pose no threat. His immortality also puts Bella's worries about Renesmee's disturbing growth rate to rest. Faced with the evidence as well as Bella's powerful shield, the Volturi take their leave. Bella, Edward, and Renesmee return to their home in peace to live happily ever after.