The book opens with Bella Swan dreaming. She dreams that she is an old woman, but Edward Cullen is still young. She wakes up on her eighteenth birthday. She is now a year older than Edward, though Edward is actually 117 years old. The Cullens have a birthday party for Bella, but when she cuts her finger on wrapping paper, Jasper attacks her, crazed by the smell of her blood. The Edward gets Jasper away from Bella, and Carlisle stitches her up.
Edward tells Bella that he and his family are leaving and she can’t come with them. Bella is so adamant about going with them that Edward tells her he doesn’t want her anymore. He makes Bella promise not to do anything reckless or stupid, and in return, promises to make it seem like he had never been a part of Bella’s life. Edward leaves and Bella tries to follow him into the woods but gets lost until Sam Uley finds her.
Bella, broken by Edward’s departure, slips into a haze for four months until Charlie tells her that if she doesn’t stop acting lifeless, he will send her back to her mother, who is in Florida. To try and appear social, Bella goes to see a movie with her friend, Jessica. After the movie, Bella sees a group of men, who remind her of a year prior when she was almost group-raped but was saved by Edward. Bella begins to approach the men and hears Edward’s voice warning her not to get any closer. After a few minutes, Bella and Jessica leave, but Jessica is upset and confused about Bella approaching the men.
Wanting to break her promise to Edward by being reckless, Bella obtains two motorcycles in need of repair and brings them to her old friend, Jacob Black, for help. He agrees to fix them in exchange for the one Bella doesn’t want. While Bella is at Jacob’s house, his friends, Quil and Embry, stop by. When they meet Bella they suspect a romance blossoming between her and Jacob. Later, when Bella leaves Jacob’s house, she no longer feels numb. The two spend more and more time together, which seems to revive Bella, though she still misses Edward and thinks about him when she isn’t around Jacob. A while later, Bella is in the school lunch room with her friends, actually listening to the conversations happening around her for the first time since Edward left. She shocks her friends when she contributes to a conversation, supporting her friend’s claims of having seen a huge bear a few days prior.
Hoping to hear Edward’s voice the way she did after the movie, Bella goes to the Cullens’ house. The property is overgrown and unused, which intensifies Bella’s pain. She does not hear his voice.
Jacob finishes the bikes, so he and Bella drive to a secluded spot where they can ride. On the way, Bella and Jacob see people cliff-diving. Realizing that cliff-diving is reckless, Bella asks Jacob to take her some time. Jacob agrees, then tells her that the people they see jumping are part of some peace-keeping gang, led by Sam Uley, the man who found Bella in the woods. Embry recently joined the gang and stopped talking to Jacob, so Jacob is suspicious of the group. Jacob teaches Bella to ride the motorcycle, but Edward’s voice tells Bella not to do something so dangerous. Bella rides the bike, thrilled that she figured out how to trigger the hallucination. She crashes and hits her head, sending her to the hospital. Jacob suggests they take a break from the bikes for a while, so they spend the next few weeks hiking in the forest. Though Bella doesn’t tell this to Jacob, she is looking for the little meadow where Edward showed her that he sparkles in the sunlight.
After a few weeks, Bella tries to get a group of friends together to go see a movie in Port Angeles, but only Jacob and Mike Newton are able to go. Both boys have crushes on Bella, making the entire movie very awkward and uncomfortable, until Mike starts throwing up due to the stomach flu. The three leave the movie early. When Jacob drops Bella off, he tells her he doesn’t feel well. The next morning, Bella wakes up with the same stomach flu as Mike. Jacob does not get the flu, but he gets sick for several days and his dad, Billy, does not let Bella visit him.
A week later, Bella calls the Blacks, and Billy tells her that Jake is better and is out with friends. Upset that Jacob didn’t so much as call her, Bella goes hiking by herself. She finds the meadow she was looking for, but it doesn’t create a hallucination like she hoped. While there, she sees Laurent, one of the vampires in James’ coven. Laurent tells Bella that Victoria, James’ mate, wants to kill Bella because Edward killed James: a mate for a mate. Laurent is thirsty, so he is going to kill Bella instead. Bella hears Edward’s voice, warning her of the imminent danger. In the nick of time, a pack of five huge wolves chases Laurent away. Bella realizes that these wolves must be the “bear” that Angela saw, which has been killing people in Forks. Bella wanders around until she finds her way out of the forest. A week later, Bella realizes that Jacob isn’t calling because he joined Sam Uley’s gang. She goes to La Push to confront Jacob, where she sees Quil, who confirms her worries. She waits for Jacob in his driveway until he appears. His hair is cut short and he is larger, more muscular than the last time she saw him. She tries to get him to open up, but he only blames the Cullens.
Later, Bella wakes up in the middle of the night to find Jacob at her window trying to get in. He tells her to try to remember the Quileute legends from the first time she met him because those will answer all her questions about him.
Bella dreams that Jacob turns into a red wolf, one of the five wolves she saw in the woods. When she wakes, she realizes that Jacob is a werewolf: an enemy to vampires. Bella gets out of bed, eager to go to La Push and talk to Jacob, but she runs into Charlie, who is on his way to hunt the wolves since they are killing people. Bella is torn between warning Jacob, her best friend, and letting Charlie punish Jacob, the murderer.
She goes to see Jake and accuses him of killing people, but he tells her werewolves to protect people from vampires. The wolves killed Laurent the day she saw them in the woods. Bella is relieved to hear that but then realizes that the vampire who is still killing people is Victoria, who is coming after Bella. Jacob calls a meeting with the other werewolves so Bella can tell them the info she knows. Paul is so upset that Jacob got Bella involved that he turns into a werewolf, set to attack Bella, but Jacob turns into a wolf to fight him.
Jared and Embry bring Bella to Sam’s fiancée, Emily’s, house. When Sam, Jacob, and Paul join them, the wolves talk about Victoria and where she will strike next. They agree to keep Bella in La Push as much as possible.
A week or so later, Jacob promises to take Bella cliff-diving, but Victoria reappears, so he cancels. Bella decides to go cliff-diving anyway to hear Edward’s voice. Though the weather is stormy, Bella jumps over the cliff, then isn’t strong enough to swim to shore. She begins to drown but is overcome with happiness. As she dies she sees Edward’s face. Jacob saves her. He tells her that Harry Clearwater, one of Billy and Charlie’s friends, had a heart-attack and is in the hospital. As they leave the beach, Bella sees a flame on the water, which she later realizes to be Victoria. Jacob takes Bella back to his house. They fall asleep. When Bella wakes up, she wonders if she could be happy married to Jacob. She realizes she needs to grow up and stop chasing hallucinations. Billy comes back and tells them Harry passed away. Bella goes home and Alice Cullen is waiting for her, which upsets Jacob. Alice, who can see the future, saw Bella jump from the cliff and thought she was committing suicide. Alice stays with Bella and Charlie for a few days. Jacob stops over as a spokesman for the werewolves and asks if the rest of the Cullens are moving back to Forks. Bella tells him no. The meeting is very tense, so Bella, upset that she was losing Jacob as a friend, begins to cry. Jacob hugs her and tells her that he will always be there for her. The phone rings, so Jacob answers and tells the caller that Charlie is “at the funeral.” Alice, who was avoiding Jacob, appears and tells Bella that Edward found out that Bella is “dead,” and is going to the Volturi to commit suicide.
Alice and Bella fly to Italy to stop Edward from killing himself. When they get to Volterra, Bella runs through incredibly crowded streets, trying to get to Edward before noon, which is when he plans to step out into the sun, exposing his sparkle-y, vampire skin to a large group of humans, which would force the Volturi to kill him. She gets to him, but he is confused, believing he is in heaven. When Bella convinces Edward that they are both still alive, they try to escape, but the Volturi force them into a building to talk to the head Volturi: Aro, Caius, and Marcus.
Aro is fascinated with Bella, and with her strong attachment to Edward. He tries to use his special power on Bella, which is to read every thought someone has ever hand by simply touching their skin, but to no avail. He then asks a member of his guard, Jane, to use her power on Bella, which is torturing people by looking at them, which also fails. He agrees to let Edward, Bella, and Alice live, under the condition that they turn Bella into a vampire someday soon. The three agree and leave.
When she returns home, Charlie is furious. Although he originally forbids Bella from ever seeing Edward again, he eventually relents, allowing her to see him during certain hours. Edward always sneaks into Bella’s room after hours. Edward tells Bella that he loves her and will never leave her again.
Edward refuses to ever turn Bella into a vampire, so Bella goes to the Cullens’ house to ask them to vote on whether or not she should become a vampire. All vote yes, except for Edward and Rosalie. Carlisle agrees to change Bella after graduation if Edward refuses to do it. Edward later tries to convince Bella to marry him first, promising to change her himself if she will.
One day, Bella and Edward are returning to Bella’s house at Bella’s curfew, and Bella’s motorcycle is out front. Bella meets Jacob in her front yard, who wanted Bella to get grounded so she wouldn’t be able to see Edward anymore. Charlie is obviously very angry at Bella for owning and riding a motorcycle, but Bella enters the house, confident that she can handle anything, now that Edward is back in her life.