The "Twilight Saga" is based on Stephenie Meyer's popular series of young adult novels revolving around new-girl-in-town Bella Swan and the love triangle she forms with vampire Edward Cullen and rival werewolf Jacob Black.
Seventeen-year-old Bella Swan moves to rainy Forks, Washington, to live with her father, the town sheriff, when her mom decides to go "on the road" with her new baseball-playing husband. Bella's a mopey, humorless teen who keeps to herself, but since 95% of high school popularity is based on looks, she falls in with the cool crowd. She's drawn to Edward, one of five pale, impeccably coifed teenaged adoptive children (along with Alice, Jasper, Emmett and Rosalie) of local doctor Carlisle Cullen. Edward initially acts repulsed by Bella, but it becomes clear that he finds her appealing but feels it's in her best interest if they don't interact. Their mutual attraction can't be contained, however, and after witnessing some of Edward's superhuman abilities, she deduces that the Cullens are vampires. Edward confirms her suspicions and explains that he can read minds, but he's intrigued by the fact that hers is blocked and that her smell is unnaturally delicious. They quickly become more than friends, as he indoctrinates her into the ways of the vampire (baseball, piggyback rides, etc.), explaining that vampires stay out of the sun not because they'll die, but because they'll sparkle so much they'll draw attention to themselves. The Cullens, we find out, are friendly, "vegetarian" vampires who feed on animals instead of humans. Trouble comes to town, however, when a trio of "old school" vamps -- James, Victoria and Laurent -- breezes through, leaving a trail of bodies in their wake. James catches Bella's scent and bites her, but the Cullens arrive to save the day, killing James. Edward must suck James' "poison" out of Bella before she's turned into a vampire. Ironically, after she recovers, she tells Edward she'd like to become a vampire, but he refuses.
The Cullens are throwing yummy-smelling Bella an 18th birthday celebration that goes awry when a paper cut triggers the Jasper's bloodlust. Taking this near feeding frenzy as a sign that Bella isn't safe around them, the Cullens decide to pack up and move out of town. Heartbroken, Bella mopes -- even more than usual -- for months before discovering that she can "see" Edward by doing something dangerous. It seems that motorcycle riding or cliff diving conjures up visions of him warning her to be careful, like Obi-Wan with dreamboat hair. Bella seeks the aid of Jacob Black, the son of an old Native American family friend, to help her repair an old motorcycle that she can use for her hallucinatory thrills, and having had a crush on her for some time, Jacob readily agrees. During the weeks-long repair process, Bella grows closer to Jacob, in part because he's become physically buff since she last saw him and in part because, well, he's there. It turns out that Jacob's physical metamorphosis -- including an increasingly volatile temper -- is emblematic of a bigger change: he's a werewolf. And, like her vampire ex-boyfriend, Jacob pushes her away when he fears for her safety. Luckily for Bella, she still has her life-threatening stunts to fall back on, but when one results in her near-death, Edward misinterprets a long-distance message to mean that she's dead. With the wisdom of a teenager, he determines to end his life too by exposing himself in the sunlight to humans, thus provoking the Volturi, the Italian vampire royalty who oversee the actions of their kind worldwide, to kill him. Bella and Alice arrive to stop him, but the Volturi demand that Bella, as a human who knows of the existence of vampires, either be killed or turned into a vampire. The Cullens promise to turn Bella, but Edward insists she marry him first.
Bella is eagerly awaiting her transformation into a vampire, and her bloodsucker boyfriend Edward is eagerly awaiting her response to his marriage proposal. Complicating matters is Jacob, who harbors a not-so-secret crush on Bella and is determined to prove that she feels the same about him. Also complicating matters is a series of murders and disappearances in nearby Seattle. Edward's clan recognizes the signs of someone building a vampire army, and it's no stretch to figure out that the vampire behind it all is Victoria, who seeks revenge against Edward for the death of her boyfriend James in Twilight. Victoria recruits a local teen named Riley to gather and train the new vamps for an attack on the Cullens. To protect Bella, Edward and Jacob have to put aside their differences and gather both the vampire and werewolf clans to defend their turf. They stop the invading army and kill both Victoria and Riley. Though the battle brings Bella closer to both Edward and Jacob, she chooses Edward, agreeing to marry him before he turns her into a vampire. But first, they have to graduate high school.
Now that Bella has made her decision, she and Edward get married and head off to consummate their union, setting off a chain of unprecedented events with potentially devastating and unfathomable consequences.