Just after Bella's (Kristen Stewart) 18th birthday, Edward (Robert Pattinson) decides to leave her behind in an effort to protect her. As the heartbroken Bella sleepwalks through her senior year, numb and alone, she discovers she can summon Edward's image whenever she puts herself in jeopardy. Her desire to be with him at any cost leads her to take greater and greater risks, including a new taste for high-speed motorcycle jaunts.

With the help of Jacob Black (Taylor Lautner), her childhood friend and a member of the mysterious Quileute tribe, Bella refurbishes a motorbike for her adventures. Bella's frozen heart is gradually thawed by her budding relationship with Jacob, who has a supernatural secret of his own.

When Bella wanders alone into a meadow, she finds herself face to face with a deadly attacker. Only the intervention of a pack of extraordinarily large wolves saves her from a grisly fate and the encounter makes it frighteningly clear that Bella is still in grave danger. In a race against the clock, Bella learns the ancient secret of the Quileute tribe and Edward's true motivation for leaving her. She also faces the prospect of a potentially deadly reunion with her beloved that is quite unlike the one she had hoped for.