Bella Swan and Edward Cullen prepare for their wedding, a highly anticipated event among their families and friends. The ceremony proceeds beautifully, leading to a joyous reception. Despite the lingering tension between the werewolves and vampires, a brief moment of peace is achieved. Following the celebration, the newlyweds depart for their honeymoon on a secluded island off the coast of Brazil. Here, they finally give in to their passions, but their joy is short-lived when it quickly becomes clear that something unusual has happened to Bella.

Bella's unexpected illness puzzles and alarms both Edward and the Cullen family. As her condition deteriorates, suspicions grow that what afflicts her is something beyond normal human ailments. Meanwhile, Jacob Black, still deeply in love with Bella, is devastated by her choice to proceed with her transformation into a vampire, a decision that cements the divide between him and his pack. Torn between his allegiance to the pack and his personal feelings, Jacob must confront his inner turmoil while Bella faces her life-altering situation at the Cullen household.