Seventeen year old Isabella Swan - Bella for short - moves from sunny Arizona to rainy Forks in Washington State to live with her father after her mother re-marries. She doesn't expect much from the small town, but she immediately becomes the center of attention: she's new, and her father is chief of police. In High School, Bella quickly makes new friends and, much to her dismay, attracts a few admirers.

During her first week in school, she notices a group of teenagers who seem different than most of the others. Their beauty is unearthly, so much so that Bella cannot help but ask about them. They are the Cullen family, five children adopted by local doctor Carlisle Cullen and his wife Esme. Bella is particularly taken by the youngest boy, Edward, who shares her biology class. However he seems so utterly repulsed by her that Bella wonders what she did wrong. Her curiosity increases when he disappears completely from school.

On his return, Edward’s behavior is no longer so cold, and he opens up a little to Bella. Their relationship deepens when Edward saves Bella from being run over in the school parking lot. This rescue, eerily superhuman, makes Bella start to suspect that Edward is not a normal human being.  She becomes determined to find out exactly what he is.

A trip to the beach offers further clues as to Edward’s nature. According to Jacob Black, a childhood friend, the Cullens are the ‘Cold Ones’, figuring prominently as adversaries in the Native American Quileute legends. They drink animal blood to survive and are immortal. Bella concludes that Edward and his family are vampires.

She confronts Edward, who reluctantly confesses the truth.  His initial coldness to her was a result of her unusual scent: her blood is irresistible to him. But he couldn't keep away from her, and now he is making a heroic effort to resist the temptation of her blood. Their mutual attraction, now that there are no more secrets between them, solidifies into love.  Edward introduces Bella to his family, and she gets to see their extraordinary physical strength, speed and talents.  This is a family that can only play baseball during a thunderstorm because hitting the ball with that much power produces a sound like a thunderbolt.

Their happiness is soon disturbed, however, when a coven of vampire nomads arrives in the area.  James, the leader, witnesses the intense relationship between Edward and the human "snack" Bella, and he vows to track her down for sport and kill her. The Cullens immediately come together to protect Bella, and she is sent to hide in Phoenix. While in hiding, Bella receives a call from James and hears her mother's scared voice on the phone. To save her mother's life, Bella slips away from the Cullens and surrenders herself, not knowing that James has tricked her - the voice on the phone was an old tape of her mother. James tortures her and bites her, infecting her with vampire venom. Just in time, the Cullens arrive to save her.  Edward has to suck just enough of her blood to remove the venom, but not succumb to the overwhelming urge to keep feeding.

After several weeks in hospital, Bella is released.  She and Edward attend the prom at Forks High School.  Bella pleads with Edward to turn her into a vampire. He refuses, and instead places a safe kiss on her neck.

The story continues in New Moon.