In Seattle, close to Forks, Victoria launches a vicious attack, inflicting a bite on Riley Biers (Xavier Samuel) to kickstart her plan of assembling an army of newborn vampires. Meanwhile, in Forks, Edward Cullen and Bella Swan engage in a heartfelt discussion regarding the challenges associated with her potential transformation into an everlasting vampire. At just 18, Bella expresses her reservations about marrying at such a young age; however, Edward insists he will not change her until they are wed, believing that she should experience life as a human first.
Bella's father, Charlie, advises her to reach out to Jacob Black, who is struggling with his own issues. Eager to help, Bella tries to visit Jacob, but Edward has sabotaged her truck, claiming the wolves are dangerous and unstable. At school, Bella is surrounded by friends, including Jessica (Anna Kendrick), Mike (Michael Welch), Angela (Christian Serratos), and Eric (Justin Chon). The Cullen family consists of Edward, Alice (Ashley Greene), Rosalie (Nikki Reed), Jasper (Jackson Rathbone), Carlisle (Peter Facinelli), Emmett (Kellan Lutz), and Esme (Elizabeth Reaser), while the werewolf pack includes Jacob, Sam (Chaske Spencer), and others, including Emily (Tinsel Korey) who is engaged to Sam.
Alice has a vision of the imminent threat posed by Victoria, who is intent on raising a legion of newborn vampires to target the Cullens and, ultimately, Bella. Aware that Victoria's reckless violence could attract the attention of the formidable Volturi, Edward urges Bella to leave Forks and stay with her mother, Renee (Sarah Clarke), in Florida. During her visit, Bella confides her love for Edward to Renee, who gifts her a sentimental quilt, pieced together from fabric that holds cherished memories.
While Bella and Edward are away, the Cullens hunt for Victoria, who cleverly eludes them by crossing into werewolf territory, forcing the wolves and vampires to clash. Upon their return to Forks, Bella meets with Jacob, who informs her about Victoria's recent actions and the chaos caused by Emmett's intrusion into wolf territory— a clear violation that prompted Edward's protective instincts. Feeling betrayed by Edward’s lies, Bella chooses to spend time with Jacob, who reveals the complexities of "imprinting," an involuntary bond experienced by the werewolves, which fuels Jacob's growing frustration when Bella declares her intention to marry Edward after graduation.
As Charlie investigates Riley's suspicious disappearance, Edward becomes increasingly convinced that the newborn vampires are behind it. Though Bella believes Jacob and the wolf pack would never put her in harm's way, Edward's protective instincts weigh heavily on him, eventually leading to a reluctant agreement for a shared guard between the Cullens and the wolves at Bella's home.
During a gathering with the tribe elders, Jacob learns about the history and capabilities of the Quileute tribe, and the ancient battle they fought against vampires, a narrative shared by his father, Billy Black (Gil Birmingham). Meanwhile, the situation escalates as Victoria and Riley build their army, generating widespread fear as murders and disappearances occur, drawing the unwanted attention of the Volturi.
This sigh of impending doom coincides with Bella’s high school graduation, and she navigates her evolving relationships as the tension mounts around her. In an effort to maintain her connection to both Edward and Jacob, Bella invites Jacob to a significant family event. However, Jacob reveals his feelings, and amidst the frustration and confusion, he kisses Bella passionately, leading to an angry reaction. Bella ultimately decides to exclude Jacob from her life temporarily, but she comes to realize she cannot deny her feelings for him.
As the Volturi make their appearance in Seattle to confront the newborn army, the Cullens realize they need to ally with Jacob and his pack to defeat the rising threat. Training begins under Jasper's guidance, who draws on his painful past with vampire armies, which helps Bella understand the peril they face. Jacob and Bella's bond continues to strengthen amid the turmoil, as she grapples with her identity and feelings for both men.
The climax builds as the newborns launch their attack, with the fateful encounter leading to intense confrontations, resulting in heartbreaking losses. Seth ultimately proves himself in battle, paving the way for Edward to confront Victoria directly. The final confrontation sees Edward outsmarting Victoria, severing ties with her after she realizes her ambition led to her downfall.
After the duel, Jane, the Volturi leader, investigates the aftermath, leading to tensions with the Cullens. Eventually, as the dust settles, Bella must reconcile her feelings as she faces her choice between two worlds. In a serene moment in their meadow, she reveals her decision to embrace Edward's way of life—marriage followed by transformation—setting a wedding date and confiding her struggles with a sense of belonging, all while grappling with the irreversible path ahead.
