Twilight is about a seventeen-year-old girl named Bella Swan, who moves from her mother's home in Phoenix, Arizona, to live with her father in her birthtown of Forks, Washington. There, she becomes intrigued by a student, Edward Cullen. When Edward saves her life, he exhibits super-human qualities. Bella learns from family friend Jacob Black that Quileute legends say the Cullen family are vampires. Edward eventually admits to this truth, though his family hunts only animals, not humans, through moralistic choice. Edward constantly warns Bella against being with him, perceiving her life to be at constant risk if she continues to associate with him because the scent of her blood is more powerful to him than that of any other human he has ever encountered. Bella's love and confidence in Edward's restraint is such that his warnings go unheeded, and on an outing with the Cullens she becomes the target of a sadistic vampire, James. With his family's help, Edward is able to save Bella from James' predations, but Edward is still unwilling to change Bella into a vampire himself
New Moon begins with Bella's eighteenth birthday. During a party at the Cullens, she gets a small paper cut while opening a present. Edward's brother, Jasper, instinctively hungering for her blood, tries to attack her. Edward realizes that his relationship with Bella puts her in danger. In a misguided attempt to protect Bella, he convinces her that he no longer loves her and moves away with his family, leaving her heartbroken and depressed for months.
To appease her worried father, Bella goes to a movie with her friend Jessica. While there, she carelessly approaches a group of rough-looking men outside a bar and discovers she can hear Edward's voice when in dangerous situations. Desperate to hear his voice again, Bella seeks out danger; she asks Jacob Black to repair two motorcycles and teach her to ride one. Their friendship grows to be very strong, and Jacob admits that he has romantic feelings for Bella, though she does not reciprocate this. When a vampire named Laurent tries to attack her, Bella is saved by a pack of giant wolves. Later, Bella learns that Jacob and other tribe members are shape shifters who assume a wolf form to protect humans from vampires. Bella also discovers that the vampire Victoria has returned to Forks seeking to kill Bella to avenge her mate, James', death.
To hear Edward's voice, Bella attempts cliff-diving and nearly drowns, but she is saved by Jacob. Edward, after being mistakenly informed by Rosalie that Bella has committed suicide, travels to Volterra, Italy, to request the Volturi to destroy him. Alice returns to Forks and discovers Bella is alive; she and Bella pursue Edward to Italy and successfully prevent him from showing himself in daylight to humans, an act that would result in his execution. The trio are taken to the Volturi. Because Bella knows about vampires, the Volturi want to kill her, but Alice claims she has foreseen Bella becoming a vampire. Because most humans are unaware that vampires exist, the Volturi threaten to kill Bella if this does not happen soon. Upon returning home, Edward reveals to Bella that he never stopped loving her, he only left Forks because he thought it would protect Bella. He apologizes for this misguided action and asks for her forgiveness, which Bella quickly grants. Bella, intent on becoming a vampire, decides that Edward's family should vote on her fate. All but Rosalie and Edward vote affirmatively for her to be changed, but Edward agrees to change her himself if she will marry him first
Eclipse continues the drama of Bella and Edward's relationship. Edward explains that he is reluctant to change Bella into a vampire because he believes that vampires are soulless creatures who have no place in heaven. Bella, whose opinion of marriage is jaded by her own parents' early divorce, agrees to marry Edward on the condition that he will make love to her while she is still human and then turn her into a vampire. He initially refuses, saying that he could easily lose control in the heat of the moment and unintentionally kill her. However, seeing how important it is to Bella, he agrees to try, but only after they are married.
The plot is driven by the machinations of the vampire Victoria, who first encountered Bella and the Cullens during the first book, Twilight. Victoria, seeking to avenge her mate, James', death, hunts Bella while building a new vampire army. To combat this threat, a grudging truce is struck between the Cullens and the Native American shape-shifting wolf pack led by Sam Uley and Jacob Black, who pits himself against Edward as a love interest for Bella. Initially, Bella considers Jacob only as a friend but, despite her engagement to Edward, she shares a kiss with Jacob and realizes she loves him as well. Ultimately, Edward accepts Bella's love for Jacob and successfully destroys Victoria. Bella acknowledges that Edward is the most important person in her life, agreeing to announce their engagement to her father.
Near the beginning of Breaking Dawn, Bella marries Edward in a wedding orchestrated by Alice. They spend their honeymoon on Isle Esme, a fictional small island that was given to Esme as a gift from Carlisle. They consummate their marriage, but their lovemaking sparks a conflict between the newlywed couple: Edward is horrified that he has bruised his new wife, but Bella insists that she is fine and wants Edward to make love to her again. He vows not to do so again while she is still human, but he eventually gives in. Soon afterwards, Bella becomes very sick and realizes that she is pregnant with Edward's child.
Edward is shocked and rushes Bella home to see Carlisle, who, as a doctor, confirms that she is expecting Edward's child. Edward goes half-crazy with worry as the rapidly growing fetus begins to drain Bella's health, and he tries to coerce her into having an abortion to save her own life. However, Bella feels a bond with her unborn child and insists on giving birth. Soon, Edward comes to love the baby as well, after he hears its thoughts and learns that the baby loves Bella in return and doesn't mean to hurt her.
Bella nearly dies giving birth, but Edward successfully delivers their baby girl and then injects his venom into her heart, thus healing her wounds by turning her into a vampire. During Bella's painful transformation, Jacob imprints —an involuntary process in which a werewolf finds his soul mate— on the baby, Renesmee.
After a vampire named Irina mistakes Renesmee for an immortal vampire child (a creation that is forbidden in the vampire world), the Volturi arrive to destroy the Cullens as punishment for the alleged transgression. Edward stands with Bella and their allies to convince the Volturi that Renesmee is not an immortal child and poses no threat to their existence. Once the Volturi leave, Edward and Bella are finally free to live their lives in peace with their daughter.
Bella is described in the novels as being very pale with brown hair, chocolate brown eyes, and a heart-shaped face. Beyond this, a detailed description of her appearance is never given in the series. Stephenie Meyer explains that she "left out a detailed description of Bella in the book so that the reader could more easily step into her shoes." While Meyer stresses that "Bella's looks are open to interpretation", she does supply her own personal interpretation on her website, describing Bella as:
"very fair-skinned, with long, straight, dark brown hair and chocolate brown eyes. Her face is heart-shaped—a wide forehead with a widow's peak, large, wide-spaced eyes, prominent cheekbones, and then a thin nose and a narrow jaw with a pointed chin. Her lips are a little out of proportion, a bit too full for her jaw line. Her eyebrows are darker than her hair and more straight than they are arched. She's five foot four inches tall, slender but not at all muscular, and weighs about 115 pounds. She has stubby fingernails because she has a nervous habit of biting them."
Bella also has a small crescent-shaped scar on her hand where she was bitten by James, a tracker vampire, in Twilight. The scar is described as being pale, always a few degrees colder than the rest of her body and sparkles slightly. After Bella is changed into a vampire by Edward Cullen in Breaking Dawn, in keeping with the appearance of most vampires, she becomes more attractive, her eyes turn red, and her already pale skin becomes even whiter.
Personality traits and abilities
Bella is described as being clumsy and stubborn. She has a private mind, which is thought to be why Edward is unable to hear her thoughts. She is also said to a terrible liar, but occasionally demonstrates good acting ability. Bella becomes faint when she smells blood, though this no longer bothers her once she becomes a vampire. Stephenie Meyer has stated that Bella's "tragic flaw" in Eclipse is her lack of self-knowledge. After being turned into a vampire, she describes having a much clearer view of the world. She is also very self-controlled, being able to ignore the scent of human blood on her first hunting trip. Bella's private mind that was able to repel some vampires' mental abilities while she was human, evolved after she became a vampire; her skill strengthened, allowing her to shield herself and those around her from other vampires' mind control. By the end of Breaking Dawn, she is able to cast the shield away from herself. She is also described by Edward as "very graceful", even for a vampire, in comparison to her earlier clumsiness.
In the film adaptations, Bella is portrayed by actress Kristen Stewart. Meyer stated that she was "very excited" to see Stewart play the part and that she was "thrilled to have a Bella who has practice [in a vast array of film genres]", since, according to Meyer, Twilight has moments that fit into many genres.