Although James left Bella alive, he is a "tracker". That means he hunts down his prey and kills it, which he thinks of as a game. He plans on tracking Bella. She goes to Phoenix, Arizona to escape the deadly vampire, but he blackmails her into going to meet him. They meet at Bella's old dance studio, where Bella learns that her mother is still safe. James almost kills her, but the Cullens save her before she is dead. They kill James and get Bella safely to a hospital. The doctors tell her that she will make a full recovery in time, though she has broken her leg.
"New Moon" starts on September 13, Bella's 18th birthday. she had been dreading this day, because it would make her older than Edward, her vampire boyfriend. An incident happens at her birthday party, and Bella gets hurt. The fresh blood is too much for Jasper, the Cullen least committed to their diet, and he tries to attack her. Carlisle, the oldest vampire of the Cullens and the one most in control of himself, fixes her wound, and then Bella goes home.
Edward believes he is putting Bella in too much danger just by being around her. The Cullens leave, and Edward says goodbye to Bella after telling her that he does not love her anymore. Before leaving, he makes her promise not to do anything reckless, and then promises her that this would be the last time she saw him. She tries to follow him after he leaves, but ends up getting lost in the woods. She is found later that night by Sam Uley, a Quileute man from the nearby Indian reservation in La Push.
After that night, Bella goes into a depressed state. She does not talk to anyone, except to answer direct questions. She does not do anything except go to school and work. This is too much for her father, and he tells her that he is going to make her go to Florida to live with her mother. Bella protests this, and to make her father happy, she and her friend Jessica go to a movie.
After the movie, Bella has a delusion in which she hears Edward's voice clearly in her head. She "wakes up" after this. She decides to break her promise to him that she would not do anything stupid. She visits Jacob Black, her childhood friend, to see if he can fix up two motorcycles that she got for free. They quickly become friends. Jacob makes Bella happy for the first time since Edward left her.
When they ride the motorcycles for the first time, Bella hears Edward's voice again. She realizes that she hears it whenever she is in danger. She hears the delusion again when she meets Laurent, the other male in James' coven. He tells her that Victoria, James' mate, is out to seek revenge on Edward for killing James. He is about to kill Bella, when five large wolves chase him down and kill him.
Bella also learns of Sam Uley the day she first rides the motorcycle. Sam Uley and his "cult," as Jacob describes them, are cliff diving (jumping off the cliff in la Push into the water below, for fun). Jacob is scared that Sam is doing something to control the young men on he reservation. When Jacob suddenly breaks off their friendship, Bella suspects that Sam has gotten to him. When Jacob sees how upset Bella is over their broken friendship, he makes her guess that he is a werewolf, because he cannot tell anyone that, and also that it is dangerous for him to be around her. He tells Bella that Sam is a werewolf, and his cult was actually a pack of the werewolves in La Push. He says that their purpose is to keep their reservation safe and they call them selves "protectors", and reveals that they were the wolves she had seen who had chased down Laurent. He tells her that they are still trying to kill Victoria.
The werewolves are hunting Victoria one day, and Bella is alone on the beach in La Push. she decides to go cliff diving. She nearly drowns in the water, but Jacob saves her. Alice "sees" Bella jump off the cliff (Alice sees visions of the future) and goes to Forks to try to help Charlie with the loss. But she finds Bella still alive, and Bella is extremely happy at their reunion.
Rosalie, the only Cullen who did not like Bella, tells Edward that Bella is dead. He plans to kill himself by going to Italy and asking the Volturi, vampire "royalty," to kill him. Bella and Alice go to Italy to show him that she is still alive. After barely escaping the Volturi, Edward, Alice, and Bella go back to Forks with the rest of the Cullens. They return to Forks, and Edward tells Bella that he was lying when he told her he did not love her, and that he would never leave her again. Bella takes the Cullens' votes, and everyone except Rosalie and Edward say she should join their family as a vampire (Rosalie had issues with becoming a vampire, and did not want Bella to make a choice she would regret; Edward was afraid that vampires had no soul or afterlife, and did not want Bella to lose her soul).
In "Eclipse", Jacob and Bella's friendship is shaken by the Cullens' return. Jacob will not visit Bella, or answer any of her telephone calls. This has Bella upset and wants to visit La Push, but she is still grounded for her sudden disappearance to Italy. Charlie blames Edward for Bella's depression, and restricted the time he spends at his house.
Charlie suddenly ungrounds Bella one day, and she is free to see Jacob. But when she plans one night to go see him, Edward has disabled her truck so she cannot go. He says that young werewolves are unsafe, that they can lose control and end up hurting those near them. Despite this, when he is away hunting, Bella goes to see Jacob.
Meanwhile, a string of murders are happening in Seattle, and the Cullens believe there is a "newborn" vampire loose in Seattle. However, as the number of murders increases, they begin to suspect an "army" of newborn vampires. Jasper tells Bella of his part in vampire wars in the South. He explained how vampires would create armies of newborn vampires to take control of cities, where there was more blood.
While Bella is away at the Cullens' one night, an intruder breaks into her house and steal some of her things, to get the scent of her blood. The Cullens do not know why or how this happened, but Bella realizes, the day of her graduation, that whoever had broken in was part of the newborn army in Seattle. He had taken her things so the others could find her.
When the werewolves find out about the newborn army, they decide to help the Cullens fight them. This greatly relieves Cullens, and the werewolves are excited about the fight. Alice, with her visions of the future, sees the newborns coming to a clearing near Forks to attack. To make sure Bella is safe, she is to go to a place in the mountains away from the fight. To make sure no one can follow her scent, Jacob Black carries her there. Edward and one of the younger werewolves would stay with her there while the battle goes on.
While the Cullens and werewolves fight in the clearing, Victoria and her "mate" Riley, follow Edward's scent to where he and Bella are. Edward kills Victoria, and he and the werewolf both help kill Riley. By the time they have done this, the fight in the clearing is over. But when one of the werewolves is attacked from behind by a newborn vampire who had been hiding, Jacob Black tries to rescue her, and gets hurt.
The Volturi arrive just after the fight is over. When the Volturi leave after a sort discussion with Cullens about what happened, Bella goes home, and then goes to visit Jacob. Bella tells him she loves him, but she loves Edward more, and cannot live without him. The epilogue is from Jacob's point of view. He receives an invitation to Bella and Edward's wedding and a note from Edward, saying that if he were in Jacob's place, he would have wanted the choice to go to the wedding. This angers Jacob, and he runs away as a werewolf, "letting Jacob Black disappear."
The book begins a few days before Bella and Edward's wedding. Jacob Black has still not returned after running away in the end of "Eclipse".