Twilight
Bella Swan moves from Phoenix, Arizona to Forks, Washington to allow her mother, Renée, to travel with her new husband, Phil, a minor league baseball player. After moving to Forks, Bella finds herself involuntarily drawn to a mysterious, handsome boy, Edward Cullen. She eventually learns that he is a member of a vampire family who drink animal blood rather than human. Edward and Bella fall in love, but James, a sadistic vampire from another coven, is drawn to drink Bella's blood. Edward and the other Cullens defend Bella. She escapes to Phoenix, Arizona, where she is tricked into confronting James, who tries to kill her. She is mortally wounded, but Edward rescues her and they return to Forks.

New Moon
Edward and his family leave Forks because he believes he is endangering Bella's life. Bella falls into a deep depression, until she develops a strong friendship with werewolf Jacob Black. Jacob and the other wolves in his tribe must protect her from Victoria, a vampire seeking to avenge her mate James' death by killing Bella. A misunderstanding occurs, and Edward believes Bella is dead. Edward decides to commit suicide in Volterra, Italy, but he is stopped by Bella and Alice, Edward's sister. They meet with the Volturi, a powerful coven of vampires, and are released on the condition that Bella be turned into a vampire in the near future. Bella and Edward are reunited, and the Cullens return to Forks.

Eclipse
The vampire Victoria (James's mate from Twilight) has created an army of "newborn" vampires to battle the Cullen family and kill Bella. Meanwhile, Bella is forced to choose between her relationship with Edward and her friendship with Jacob. Edward's vampire family and Jacob's werewolf pack join forces to successfully destroy Victoria and her vampire army. In the end, Bella chooses Edward's love over Jacob's and agrees to marry him.

Breaking Dawn
Bella and Edward are married, but their honeymoon is cut short when Bella discovers she is pregnant. Her pregnancy progresses rapidly, making her weak. She nearly dies giving birth to her and Edward's half-vampire-half-human daughter, Renesmee, but Edward injects Bella with his venom to save her life by turning her into a vampire. A vampire from another coven sees Renesmee and mistakes her for an "immortal child", whose existence violates vampire rules, and informs the Volturi. The Cullens gather vampire witnesses who can verify that the child is not one of the immortal children. The Cullens and their witnesses convince the Volturi that Renesmee poses no danger to vampires or their secret, and they are left in peace.