Bella awakens from her transformation from human to vampire, not only keenly aware of her new abilities, but also of changes within the coven as Jacob has imprinted on her child, Renesmee. It also appears that Bella's father, Charlie, has been attempting to contact the Cullens for updates on Bella's illness. They intend to tell him she didn't survive, which requires that they move out of Forks, Washington to protect their identities. Jacob, desperate not to lose Renesmee, tells Charlie that his daughter is in fact alive and well, and explains that Bella has had to change in order to survive. He morphs into a wolf, revealing his tribe's shape-shifting power, but does not tell Charlie about vampires, stating that Bella just had to change into something "other".
Several months pass uneventfully, with Carlisle monitoring Renesmee's rapid growth with Bella, Edward, Jacob and the rest of the Cullen family worrying what will become of her with such a rapid growth rate. On an outing in the woods, a bitter Irina sees Renesmee from a distance, and believes her to be an immortal child. Immortal children were those who were frozen in childhood, and because they could not be trained nor restrained, they destroyed entire villages. They were eventually executed, as were the parents who created them, and the creation of such children outlawed. Irina goes to the Volturi to report what she has seen to them.
Alice sees the Volturi and Irina coming to kill the Cullens, and leaves with Jasper the next day, instructing the others to gather as many witnesses as they can that can testify that Renesmee is not an immortal. They must gather the witnesses before the snow covers the ground, because that is when the Volturi will come. The Cullens begin to summon witnesses, such as the Denali family. One of the Denali, Eleazar, later encounters that Bella has a special ability: a powerful mental shield, which she can extend to protect others from mental attacks like those from Jane and Alec, with practice.
As some of their potential witnesses are attacked and prevented from supporting the Cullens, Carlisle and Edward realize they may have to fight the Volturi, despite their desire to avoid this. Some witnesses hesitate, but ultimately agree to stand with them in battle.
The Volturi arrive, led by Aro, who is eager to obtain the gifted members of the Cullen coven as part of his guard. Aro is allowed to touch Renesmee, and is convinced that she is not an immortal child. Irina is brought forth and she takes full responsibility of her mistake, leading to her immediate death. Her sisters are tempted into picking a fight, but are restrained. Although the blunder has been settled, Aro still insists that Renesmee may pose a risk in the future. Alice and Jasper appear to attest to the existence of other children like Renesmee, and Alice shows Aro a vision of the future. In the vision, Aro refuses to change his decision and a battle ensues, during which both sides undergo heavy casualties, with most of the Volturi dying. The identifiable major characters who die in the vision are (for the Cullens) Carlisle, Jasper, Seth, Leah and (for the Volturi) Aro, Jane, Alec, Caius, Marcus, Demetri and Felix. After the vision ends, Alice reveals to Aro that the vision will come to pass if Aro maintains his pursuit of Renesmee. Two more witnesses then arrive: a fully grown vampire-human hybrid and his aunt who have been living peacefully and undetected for 150 years, proving Renesmee is not a threat. (In a change from the novel, his three hybrid half-sisters and the gender differences in vampiric qualities of hybrids are not mentioned) For the sake of self-preservation, Aro orders his guards to retreat but not without giving one final glance to Alice and Bella.
Back at the Cullen home, Alice glimpses into the future, seeing Edward and Bella together with Jacob and a fully matured Renesmee. Edward reads Alice's mind and feels happy that Renesmee has Jacob to protect her. Alone in the meadow, Bella finally allows Edward a peek into her thoughts. As the two share a kiss, their story closes as a book revealing the final line, "And then we continued blissfully into this small but perfect piece of our forever."