Bella Swan moves from sunny Phoenix, Arizona to rainy Forks, Washington to live with her father, Charlie, while her mother, Renée, travels with her new husband, Phil Dwyer, a minor league baseball player. Bella attracts much attention at her new school and makes friends quickly. Much to her dismay, several boys compete for shy Bella's attention.
When Bella is seated next to Edward Cullen in class on her first day of school, Edward seems utterly repulsed by her. He disappears for a few days, but warms up to Bella upon his return; their newfound relationship reaches a climax when Bella is nearly crushed by Tyler's van in the school parking lot. Edward saves Bella when he comes to her rescue and stops the van with only his hands.
Bella annoys Edward with questions about how he saved her life. She hears that Edward and his family are vampires who drink animal blood after being told the legends of the local tribe by Jacob Black (a character who becomes more important in the later books in the series). Bella is saved by Edward again in Port Angeles when she is almost attacked, and Edward appears in his shiny silver Volvo. He then takes Bella to dinner and then on the drive home she tells him a theory that he is a vampire. Edward tells her that he tried to stay away from her at first because the scent of her blood was too desirable to him. Over time, Edward and Bella fall in love.
Their relationship is affected when a nomadic vampire coven arrives in Forks. James, a tracker vampire who is intrigued by the Cullens' relationship with a human, wants to hunt Bella for sport. The Cullens attempt to distract James by separating Bella and Edward, and send Bella to hide in a hotel in Phoenix. There, Bella receives a phone call from James, who claims to be holding her mother captive (which she later realizes was a trick). When Bella surrenders herself, James attacks her. Before James can kill her, Edward, along with the other Cullens, rescues her and destroy James, but not before James bites Bella's hand and snaps the bone in her leg. Edward successfully sucks the poison from her bloodstream and prevents her from becoming a vampire, after which she is taken to a hospital. Upon returning to Forks, Bella and Edward attend their school prom, and Bella expresses her desire to become a vampire, but Edward refuses.
Bella's desire to become a vampire increases throughout the series, but Edward refuses each time because he hates being immortal. He does not wish this upon Bella.
- Isabella Swan - Isabella, who prefers to be called Bella, is a 17-year-old girl. She leaves Phoenix, Arizona and moves to Forks, Washington to live with her father, Charlie so her mother can move to Florida with her new baseball-playing husband. She meets Edward Cullen in Forks High School and is immediately attracted to him. Bella uncovers Edwards secret with the help of Jacob Black; Bella and Edward venture into their forbidden love, with Edward fighting against his thirst for Bella's blood. Bella has a kind and awkward personality that is more mature than most girls her age. She is highly inttelligent and observant, noticing and then formulating theories about the Cullens' strange behaviors, physical features, and unusual abilities. At the novel's beginning, Bella finds, "the hardest part is making a decision, but once the decision is made, [she] can easily follow." As the novel progresses, Bella unconsciously learns how to make difficult choices and accept their consequences.
- Edward Cullen - Edward is a 109-year-old vampire who was transformed by Carlisle Cullen when he was near death with Spanish Influenza in 1918. He has a supernatural gift for reading people's minds. When he met Bella, he was immediately attracted to her because her thoughts are unreadable to him, and also to her strongly appealing blood scent. In New Moon Edward tries to avoid Bella for her own safety, but fails. He notices Bella's attraction to him and warns her that he is dangerous. Eventually, he confesses the truth about himself to her. Since Edward's transformation into a vampire, he had never fallen in love nor believed that he needed to. He later realizes that his existence was completely pointless and without an aim. In Bella he finds compassion, love, acceptance and care. In Twilight, Edward has a pessimistic personality influenced by Meyer's naturally pessimistic character. His character was also influenced by Mr. Rochester of Jane Eyre who also sees himself as a monster.
- James - James is a vampire with an unusual ability to track people, whether humans or vampires. His competitive character loves a challenge, and Bella's scent appeals to him. When the Cullens react to defend her, James wants to take on the biggest game of his life, knowing that by hunting Bella, the Cullens will oppose him. James tracks Bella to Phoenix, and phones her to say that he has captured her mother and is keeping her in Bella's old ballet school. Bella goes there, unaware that her mother is actually safe in Florida. At the studio James reveals that in the 1920s he hunted a then-human Alice, whose blood smelled even better than Bella's. She was saved by a kindly old vampire who changed her into a vampire. James bites Bella, injecting his venom into her wrist. The Cullens arrive in time to save her and destroy James.
- Jacob Black - Young Jacob Black may be a Bella's favourite non-vampire friend. He's a Quileute Indian and lives on La Push reservation, not that far from Forks. Upon first meeting, Bella is genuinely charmed and impressed by Jacob in many ways - he's a breath of fresh air compared to how clingy and suffocating Bella considers her Forks friends. Jacob and Bella's initial connection is that Jacobs dad, Billy, is friends with Charlie and Bella's truck used to belong to Billy. Bella goes on to learn that Jacob is really into rebuilding and fixing cars. Fairly quickly in the novel Jacob learns that he is similar to Bella in many ways. Charlie sees that Jacob is safe boyfriend material, the kind of guy Charlie would approve Bella dating.
- Carlise Cullen - Carlisle is an incredibly handsome, conscientious, morally-sound doctor. As patriarch of the Cullen clan, Carlisle started the whole 'vegetarian' (no human) diet. Carlisle is a vampire with a conscience. As a human in the 17th century, Carlisle was the son of an ardently anti-'evil-being' (witches, vampires, werewolves, etc.) pastor. Carlisle followed in his father's footsteps and hunted and killed these 'monsters'. While chasing down a vampire, he was bitten. After hiding in a pile of rotting potatoes while he underwent his painful transformation into a vampire, Carlisle realised what had happened. Horrified at what he had become, he tried for years to kill himself before deciding to hunt only animals. He gained enough self-control that he could even handle being around human blood, and eventually became a doctor.