The book then switches perspectives to Jacob's, as he receives news of the Cullens' return. Carlisle had told Charlie that Bella cannot see anyone because she contracted a rare disease in South America, and is being quarantined. Jacob assumes the worst (that Bella has been bitten and changed), and is upset when Sam Uley, acting Alpha of the pack, declares that the pack will not retaliate.
Jacob, full of anger, decides that if the pack will not retaliate collectively, that he alone will. He runs to the Cullens, contemplating how to attack. When he arrives, however, he realizes that things aren't as he expected. Bella, as opposed to being a newborn vampire, is already heavily pregnant with Edward's child. Everyone realizes that the child's rapid growth is starving Bella, as anything she eats is thrown right back up. Tensions are running high in the Cullen household as Rosalie steadily supports Bella's decision to have the child and aids her in every way possible, while Edward is furious at her intentions, which divides the family.
When Jacob returns to the pack, he informs them of Bella's child. It causes fear and anger among the werewolves, who don't know how this child might act, being the off-spring of a vampire. Sam commands the pact in the double-timbre of the Alpha, to obey his decision to destroy Bella and her unborn child. Jacob, feeling it is the wrong way to go about things, revolts and assumes his inherited Alpha position and leaves Sam's pack. Seth and Leah Clearwater soon join Jacob's pack, and it is discovered that the collective mind of the packs are separated, and neither can hear the other pack's thoughts while Jacob and Sam are Alphas. The three patrol the Cullens' territory as a means to warn them of any impending werewolf attack. Esme treats them like she would treat any of her children and provides them with food and clothes, seeing how their clothes are too often destroyed by phasing. As the werewolves spend this time together, Jacob and Leah learn to tolerate each other, as each forms a more complete understanding of the other.
As the baby continues to grow abnormally fast, Bella's health worsens. Her stomach is bruised in multiple places from the baby's movement, her ribs get cracked, along with her pelvis, and she has an unhealthy pallor. Her body begins to reject human food, and Jacob sarcastically thinks about the "creature" wanting blood. Edward overhears this thought, and the Cullens allow Bella to sample some donated, human blood. To Bella's surprise, the blood smells and tastes appealing, and revives her to an extent. During Bella's pregnancy, Edward realizes he can read the child's mind, and is astonished to discover that it already loves Bella. Edward's position changes as he hears his child's thoughts, and finally begins to love it as Bella does.
Jacob struggles with his feelings for Bella. Every time she sees him, she is outrageously happy, and this confuses Jacob. At first, he says to Leah that he doesn't want his feelings for Bella to just disappear, but eventually things become too difficult for him to handle. He tries to imprint on random girls he sees in a park, but nothing happens.
Eventually, Bella goes into labor approximately a month after the honeymoon. The hard placenta that surrounds the child cracks, and Bella begins vomiting blood. The child breaks free, with Bella very near death. Edward delivers the baby, a girl, and sets to work on making Bella a vampire. He injects his venom into her heart and bites her in several places. Jacob and Edward perform CPR to try to keep Bella's heart beating.
Jacob, believing Bella dead, leaves the room and goes on a rampage to find the baby whom he holds responsible. He finds her in Rosalie's arms, but takes one look in the baby's eyes, exactly the color of Bella's, and he imprints on her.
This book begins with Bella's pain. She is undergoing the transformation from human to vampire, and experiences an intense, mind blowing burning sensation. She finds herself unable to move, and this is due to the morphine that had been put in her system in an attempt to dull the pain. As the pain begins to wear off, so too does the limiting effect of the morphine, but Bella remains as still as possible to prevent Edward from feeling guilty and agonized over her pain. Bella can overhear pieces of conversation near the end of the transformation.
When she opens her eyes, she feels a warm hand on her. She is startled, and moves instinctively to a defensive position. She realizes that Edward now feels relatively warm to her, and that she has just become a vampire. The Cullens are wary of Bella, who is supposed to be unstable as a newborn, yet Bella manages to show some self-control unseen in most newborns. She wishes to see Renesmee, her daughter, but is unallowed, due to the fact that Renesmee is part human, and the family believes Bella will be unable to deny her newborn thirst if she sees the child so soon, and without hunting.
Edward decides to take Bella on her first hunt to ease her thirst. Before they go out, Alice shows Bella her reflection. She is stunningly beautiful, but not "herself" as when she was human, and has red eyes. Bella experiments with her new body on the hunt. She is graceful, strong, and fast. While hunting, she accidentally crosses a human scent, but resists the urge to kill and runs away to avoid bloodshed. Edward is astounded, as a hunting newborn shouldn't be able to deny their instincts just yet.
Upon returning, Bella is allowed to see her daughter, in part because of the recent encounter with the human scent in the woods. Renesmee has already grown astonishingly fast, and looks older than she should be. Bella learns of Renesmee's gift - the ability to communicate by sending images to people's minds through touch. Bella becomes furious when she learns that Jacob has imprinted upon her daughter, and attacks him, breaking Seth's collarbone and shoulder when he steps between the two. Eventually, she manages to calm down.
The Cullens give Bella and Edward a cottage for Bella's birthday that is not too far from the Cullen's house, for them to live in with their baby. That night, Bella and Edward make love for the first time since Bella has been changed and is equal to Edward. They find it very difficult to satisfy their desire for one another, something Edward tells Bella is normal for vampires when they begin a physical relationship, which usually takes years to control.
Edward and Bella's baby, Renesmee, matures quickly and soon is able to speak, walk and hunt. The baby also leads to a truce between the Quiletes and the Cullens because of Jacob's imprinting. Differences between the two packs are soon settled as well, with Jacob leading them.
Unfortunately for the Cullens, the Volturi have made their decision to come after them and are given a premise by Irina from the Denali clan. After seeing Bella and the baby (Renesmee), Irina assumes that Renesmee is a forbidden immortal child. The Cullens know that Irina was mistaken and decides the only way to stall the Volturi long enough to explain is to build a following of their own.
Alice suddenly leaves the Cullen's with Jaspar, leaving a note on a cover page of Shakespeare's The Merchant of Venice, which Bella recognizes as a sign to her and her alone. This leads Bella to forge fake documents just in case she needs Jacob and Renesmee to escape. During all this time, nomadic, vegetarian, and clans of vampires arrive on the Cullen's land after the family begins seeking out their friends to help with the Volturi. They all take a liking to Renesemee and agree to bear witness to the Volturi that she is not an immortal child.
Bella also discovers her power of mind-privacy has a shielding effect she could possibly carry to others. During the month of preparation for the Volturi, several of the vampires with quantifiable supernatural talents help her learn to expand the barrier, which comes into great effect as the Volturi come for confrontation. The Volturi, seeing they were misinformed, are not satisfied to leave because they want to fight and take the vampires with gifts for themselves. But Bella's gift disables the Volturi's offensive fighters, Alec (who causes one to lose their senses) and Jane (who creates the illusion of pain in the victim). During the confrontation, the entire Volturi family and guards are shocked to find so many vampires against them, as well as the wolves. Before they leave, they reveal that the so-called werewolves are not actual werewolves, but rather "shape shifters," who adapted to only be able to shift into wolf forms.
Just before Aro, Caius, and Marcus can vote to either destroy them or leave, Alice and Jasper return as well with more evidence from South America that Renesmee would not grow up to become a danger to the vampire world. Facing no choice Aro chooses to give up the fight, and the Volturi flee. The vampires celebrate their victory, along with Edward and Bella, who have successfully protected their child.
The book concludes with a "Happily Ever After" chapter for Bella, Edward, Renesmee, Jacob, and the rest of the Cullens. After leaving the Cullens' home for their own, Bella and Edward tuck Renesmee into her bed and head off to their bedroom arm in arm and happy. Bella tells Edward she wants to try something with him, that she wants him to see her human memories, even though it did not work so well when she tried it with Zafrina. She places her hands on his cheeks and tries to push her shield away, bringing up all of the specific memories she wants to see, and it works. She shows Edward special moments between the two of them from her perspective, letting Edward see for the first time just how deeply she loves him through her memories. Edward is thus unable to control himself from kissing her, and breaks her concentration and so she stops, but she tells him that now he knows that no one loves anyone as much as she does him. He asks her if she can do it again, and she tries, but he still can't resist kissing her. The book ends saying And then we continued blissfully into this small but perfect piece of our forever.