It is revealed that Bella's truck had "died a natural death." Her replacement car is a Mercedes Guardian. It is Edward's belief that Bella needs this armored sports car because of how accident prone she is. Even though she is happy about marrying Edward, she still feels guilty because she feels that her rejection caused Jacob to run away at the end of Eclipse. She and Edward also tell Charlie about their engagement. He accepts it, but reminds them that they still have to tell Renee, Bella's mother, about the engagement. Renee is also receptive to the news. Edward's sister, Alice plans the wedding and the party is just as extravagant as her other parties. Also, Bella gets an extra wedding present: Jacob, despite his broken heart, has decided to come after all. Pretty soon though, Bella slips and tells Jacob that she and Edward plan on making love on their honeymoon. Jacob, overcome with anger, becomes violent towards Bella and Edward and has to be led out by the wolf pack.
Bella tries not to let her disappointment spoil her wedding day, and she and Edward soon depart for their honeymoon to an island off the coast of Brazil. The island was a gift from Carlisle to Esme. Once there, Edward fulfills Bella's wish and makes love to her. In the morning, they argue because Edward's passionate love making had left dark bruises all over her body. She does't care but Edward refuses to make to love to her again until after she is a vampire. In an attempt to dampen Bella's love making appetite, they engage in physically exhausting activities outdoors day after day. Bella still begs Edward to make love to her, he continually refuses, not wanting to hurt her again. He soon succumbs to her and they cautiously make love. This time, Bella is unhurt.
Soon, Bella starts having strange dreams in which she finds her friends dead atop a pile of dead bodies, in the dream she also feels a strange desire to protect a strange, green eyed boy. Also, Bella finds herself constantly sick and craving food. She soon finds a box of unused tampons and realizes she is pregnant.
Though Bella has never longed for a child, she instantly becomes attached to the baby growing inside her. Edward, however is only concerned for Bella's health. After hearing stories from the local woman (who has long suspected that Edward is a vampire) of similar situations in which the mother dies, Edward wants to get rid of the baby. Edward makes plans to bring Bella home where Carlisle will "take care of it."
Bella doesn't want to lose the baby, she doesn't voice these objections to Edward, but she calls Rosalie, who has always longed for a child. On the way home, Bella is silent and Edward only figures out the plan when the plane lands and he is able to hear Rosalie's thoughts.
The book is now told from Jacob's perspective as he receives news of Bella and Edward's return. Carlisle has advised Charlie that Bella cannot have any visitors because she has picked up some rare disease in South America and is quarantined. Jacob assumes that Bella has been changed into a vampire and he is outraged when Sam Uley, acting as werewolf alpha, forbids the wolf pack from attacking the Cullen's.
Jacob decides that if the pack will not act collectively, he will act singly. Forming strategies in his mind as he is running to the Cullen's, he is shocked when he gets there to discover that Bella is not a newborn vampire, but heavily pregnant. Everyone realizes that this baby is starving Bella and bruising her. She cannot digest any food and vomits after eating anything. Tensions are high in the house because Rosalie is supporting Bella in her decision to keep the baby, and Edward is furious with Rosalie. Jacob also is mad at Edward for impregnating Bella. Jacob also agrees to kill Edward if Bella dies.
When Jacob returns to the pack, he ends up informing them of the pregnancy through the mental pathway they share among each other. Sam immediately declares war on the Cullen's, declaring they have no choice but to kill Bella to kill the baby. Sam commands the pack in the double timbre to obey and kill Bella and the baby. Jacob, who is still in love with Bella, disagrees. But Sam takes his will away from him. Jacob counters this by taking his rightful position as alpha. This almost leads to Sam and Jacob fighting for the right to rule, but Jacob leaves the pack before this happens. Seth and Leah Clearwater also join Jacob in his fight to protect the Cullen's. Losing the element of surprise and pack members and not wanting to fight against their own kind, dissuades Sam from mounting an attack. It is also revealed that Jacob and his old pack are no longer mentally connected; members of two different packs cannot hear each others thoughts.
Jacob, Seth and Leah, patrol the Cullen's territory to forewarn them of any impending attack. Esme gratefully provides them with clothing and food. As Jacob and Leah spend time together, they learn to tolerate each other as they each form understandings of each other.
Knowing that this pregnancy is endangering Bella's life and not wishing to deny her the chance of experiencing child birth and motherhood, Edward asks Jacob to make love to Bella and have a baby with her. Jacob is shocked that Edward would suggest such a thing and doesn't want to, but he also finds the idea highly tempting and agrees to mention it to Bella. For her part, she doesn't know exactly what he means, but when she finally grasps it, she is touched by Edward's concern, but also refuses the offer because she finds it repulsive to sleep with someone other than Edward or have anyone else's baby.
As the fetus continues to grow, Bella's health worsens. Her stomach is bruises in multiple places from the baby's constant movements. Two of her ribs crack, her pelvis is almost broken, her pallor is unhealthy. Her body continues to reject human food, and Jacob sarcastically makes a comment about the fetus needing blood. Edward overhears the thought and Carlisle lets her sample some donated blood from the hospital. Bella's strength returns almost instantly. To Bella's surprise, the blood tastes and smells appealing. Edward also realizes that he can read the baby's mind and begins to love the baby just as much as Bella does. This leaves Jacob feeling betrayed because he had counted on Edward to hate the baby more than he did.
Jacob struggles with his feelings for Bella. She is always outrageously happy to see him whenever he comes, and this only makes him feel more confused, he asks her about this, and she tells him that she's always thought of him as part of her family. This only makes Jacob feel worse, because he does't think he could be part of her family since she chose Edward over him. Leah suggests that Jacob go out and find the girl he's meant to imprint on, so he won't suffer anymore. Jacob doesn't want his feelings for Bella to disappear, but things eventually become too hard for him to handle, and Edward throws him the keys to an Aston Martin.
Jacob arrives at a park, where he tries to imprint on random girls, but nothing happens. He spots a girl named Lizzie, and he is impressed by her niceness and knowledge of cars, but, again, nothing happens. After returning to the house, Edward approaches Jacob in the garage. He asks for Jacob's permission, as Ephraim Black's heir, to bite Bella once she gives birth. After Jacob thinks it through, he agrees, realizing that it was the only way to save Bella.
Bella goes into labor nearly a month after the honeymoon. The hard placenta that surrounded the baby, cracks. She begins vomiting blood. The baby breaks free and Bella is near death. Edward delivers the baby, a girl, and injects a syringe filled with his venom into Bella's heart. He also bites her in several places to insure the transformation is complete. Jacob and Edward both perform CPR on Bella and eventually Jacob comes to believe that Bella is dead and is viciously sent away by Edward.
Mad with rage over Bella's supposed death, Jacob rushes down the stairs intending to kill the baby who he hold responsible. He finds her in Rosalie's arms, but before he can attack her, he imprints on the baby. He sees that the baby has the same exact eyes as Bella.
The book is, again, told from Bella's perspective. She is in the middle of being changed into a vampire. After receiving an injection of morphine, Bella is unable to move. As the effects of the morphine begin to thin, Bella tries to remain as still as she can, so she doesn't make Edward feel any guiltier than he already feels.
When she wakes up, she feels a warm hand on her, and reacts instinctively, only to realize that it's only Edward. Now his hand would feel warm to her and she realizes that she is finally a vampire. The Cullen's are wary of her, because newborns are always unpredictable and volatile. But Bella manages to show self-control that is unheard of in newborns.
She wants to see her daughter, Renesmee, who is named after Bella's mother, Renee, and Edward's mother, Esme. Because Renesmee is part-human, the Cullen's are wary of letting Bella near her until after she's hunted.
It is their belief that Bella will be unable to deny her newborn thirst if she sees the baby without first hunting. Edward takes Bella hunting, but before Alice shows Bella her reflection in a mirror and Bella is shocked to discover she has been transformed into a stunningly beautiful woman and flawless skin and vampire red eyes. Bella jumps out the window, kicks off her shoes and goes barefoot. She is now strong and graceful, and strong. She accidentally catches the scent of hikers, she resists the urge to kill them and runs away to avoid bloodshed. Edward is astounded because newborns cannot typically deny their instincts.
When she returns from hunting, Bella is finally allowed to meet her daughter for the first time. Because Renesmee is growing at an astonishing speed, she looks older than her real age. Bella also learns of Renesmee's gift-the ability to communicate by touching that individual and sending messages into their minds.
Bella is furious to learn that Jacob has imprinted on Renesmee and tries to attack Jacob. Her strength is tested, but she manages to avoid attacking Jacob, until she learns that he has nicknamed Renesmee "Nessie," the nickname of the Loch Ness Monster. She loses her self-control and tries to attack Jacob, but Seth jumps in the way, and Bella accidentally breaks his collar bone and shoulder.
Bella and Edward receive a cozy cottage for her birthday. Esme had designed and renovated it for them. Once there, Bella and Edward make love for the first since Bella's transformation. They both find it very hard to fully satisfy their sexual yearning for each other. At first, sexual desire cannot be attained. Edward tells Bella that it takes years for that kind of control to be achieved.
Renesmee continues to mature quickly and soon she is able to speak and walk. Jacob's imprinting on Renesmee, also forces Jacob and Sam to make true peace. Since an object of a wolf's imprint can never be killed, the two packs are able to live in relative peace. The differences between the two packs are settled. Jacob and Sam agree to become co-existent alpha's. Also, Quil and Embry join Jacob's pack. Jacob soon learns that the Cullen's plan on leaving Forks, thinking that Charlie is the reason, Jacob phases in front of him. He tells Charlie about Bella's change and Renesmee. Bella is furious, thinking that Charlie will now either have to die or be turned into a vampire, but Charlie told Jacob and Bella not to tell him more than he needed to know.
Peace lasts for several months than things start to unravel again: Irina, one of their friends, sees Jacob and Renesmee playing in the woods and was too far away to hear the heart beat of Renesmee. She thinks that Renesmee is one of the forbidden immortal vampire children and goes to tell the Volturi about the child. The immortal children had been banned because of their inability to control themselves and the secret.
The Cullen's know Irina was mistake and start collecting reliable witnesses. After leaving a note from a book of The Merchants Of Venice, Alice and Jasper suddenly leave the Cullen family. Since the couple does not provide a warning or a reason why, the Cullen family does not know why they have fled. Since it was Bella's copy of the book, Bella sees it as a sign from Alice. She returns to the cottage and discovers a note that Alice had written to her with a name and an address. Bella discovers that the address belongs to a lawyer named, Jason Jenks, who specialized in forging illegal documents. Bella requests fake documents for Jacob and Renesmee. Vanessa Wolfe for Renesmee-should they need to escape if a fight ensues with the Volturi.
Meanwhile, all the Cullen's friends are enthralled with Renesmee and almost all agree to witness to the Volturi that she is not an immortal child. Bella also discovers that her power is a strong shield that can wrap itself around the people she intends to protect. Several of their friends also teach Bella how to expand the power.
When the Volturi finally arrive, the Cullen's and their friends and the wolf pack stand together. The Volturi discover that they have been misinformed and execute Irina for her mistake, However, the Volturi are not satisfied to leave because they don't know if Renesmee will become a threat in the future. Aro wants to convince Renesmee he has no intention of killing her friends and family, but the Cullen's aren't sure if he's lying or not. Bella's gift disables the defensive fighters, Alec-who can cause one to lose all senses.
Jane-who can cause a victim great pain, even though it's all in their minds. Aro, Caius and Marcus vote on whether or not Renesmee will be a danger once she attains maturity. Just before Aro casts his vote, Alice and Jasper appear in the clearing with two of their own witnesses. Two witnesses who are just like Renesmee. One vampire is around a hundred and fifty and lives in South America. He and his three half-sisters, (who are all half-vampire, half-human), are all part of a super race are the children of a vampire who is creating a super race. They have never caused any harm to the vampire world. Facing no other choice, Aro calls off the fight. Before he leaves, he reveals that the werewolves aren't actually werewolves, but actually shape-shifters who could actually change into anything they wanted, but the werewolf form is the one they chose.
After a short celebration with friends and family, Bella and Edward return to their cottage where they tuck Rensemee into bed and Bella is able to let down her shield and let Edward hear her true thoughts. Hear how much she loves him. Edward is unable to control himself and kisses her, he breaks her concentration. She stops. She tells him that now he knows no one loves anyone as much as she loves him.
He asks if she can try again, she agrees, once again, abandoning restraint, Edward kisses her, Bella reminds him that they have forever to perfect it and the the book closes with, "and then we continued blissfully into this small but perfect piece of our forever."