The story begins with the revelation that Seattle is being plagued by a string of unsolved murders, which Edward suspects to be the cause of a newborn vampire that is unable to control its thirst. Edward and Bella fill out college applications, while Bella explains to Edward her desire to see Jacob, her werewolf friend, again. Meanwhile, Alice Cullen has a vision that Victoria, a vampire that is hunting Bella, is back in town.
Although Edward fears for her safety, Bella insists that Jacob and the rest of the werewolf pack would never harm her, but Edward is still not convinced. While Edward and his brothers leave town to hunt, Alice, Edward's sister, is left to "babysit" Bella. During school, Bella runs off with Jacob. When Bella arrives afterwards at the Cullens' house unharmed, Edward is convinced that the pack of werewolves were harmless to her and allows Bella to visit Jacob once in a while. During one of these visits, Jacob reveals to Bella that he is in love with her and forcefully kisses her, much to her displeasure. She reacts by punching him, succeeding only in breaking her hand. Edward angrily threatens Jacob when Bella is brought back home, saying that if he ever kisses Bella again without her permission, he will break his jaw. Later that night after Jacob leaves, Bella tries to get Edward to sleep with her before turning her into a vampire. Edward initially refuses, explaining to Bella that he could very easily kill her. Eventually, upon realizing how much it means to Bella, he says that he is willing to try in the future as long as they are married first. Despite having an aversion to marriage, Bella realizes that spending eternity with Edward is more important to her than anything else and accepts his proposal.
Bella and the Cullens realize that the murders in Seattle are being committed by Victoria and an "army" of newborn vampires. The Cullen family joins forces with the werewolf pack in order to combat this threat. As everyone else prepares for battle, Edward and Bella camp up in the mountains, where they are later joined by Jacob and Seth Clearwater– a young member of the werewolf pack– to wait out the fight. In the morning, Jacob overhears Edward and Bella discussing their engagement and becomes very upset. He threatens to join the fight and get himself killed because Bella doesn't love him; when Bella begs him not to, Jacob insists that he won't do so if she asks him to kiss her. Furious, she does so, and while kissing him she realizes that she is in love with him as well. However, she explains that her love for Edward is much greater and that she cannot live without him.
The Cullens, as well as the werewolf pack, suffer no casualties during the fight and successfully destroy Victoria and her army.