Breaking Dawn is split into three separate parts. The first part details Bella's marriage and honeymoon with Edward, which they spend on a private island off the coast of Brazil. Two weeks into their honeymoon, Bella realizes that she is pregnant and that her condition is progressing at an unnaturally accelerated rate. After contacting Carlisle, who confirms her pregnancy, she and Edward immediately return home to Forks, Washington. Edward, concerned for Bella's life and convinced that the fetus is a monster as it continues to develop with unnatural rapidity, urges her to have an abortion. However, Bella feels a connection with the child and refuses.
The novel's second part is written from the perspective of wolf shape-shifter Jacob Black, and lasts throughout Bella's pregnancy and childbirth. Jacob's Quileute wolf pack, not knowing what danger the unborn child may pose, plan to destroy it, also killing Bella. Jacob vehemently protests this decision and leaves, forming his own pack with Leah and Seth Clearwater. Bella soon gives birth, but the baby breaks many of her bones and she loses massive amounts of blood. In order to save her life, Edward changes her into a vampire by injecting his venom into her heart. Jacob, who was present for the birth, almost immediately "imprints"—an involuntary response in which a shape-shifter finds his soul mate—on Edward and Bella's newborn daughter, Renesmee.
The third section of Breaking Dawn shifts back to Bella's perspective, finding her changed into a vampire and enjoying her new life and abilities. However, the vampire Irina misidentifies Renesmee as an "immortal child", a child who has been turned into a vampire. Because "immortal children" are uncontrollable, creating them has been outlawed by the Volturi. After Irina presents her allegation to the Volturi, they plan to destroy Renesmee and the Cullens. In an attempt to survive, the Cullens gather other vampire clans from around the world to stand as witnesses and prove to the Volturi that Renesmee is not an immortal child. Upon confronting the gathered Cullen allies and witnesses, the Volturi discover that they have been misinformed and immediately execute Irina for her mistake. However, they remain undecided on whether Renesmee should be viewed as a threat to vampires' secret existence. At that time, Alice and Jasper, who had left prior to the confrontation, return with a Mapuche called Nahuel, a 150-year-old vampire-human crossbreed like Renesmee. He demonstrates that the crossbreeds pose no threat, and the Volturi surrender. Edward, Bella and Renesmee return to their home in peace.