Plot
16-year-old Ethan Wate lives in Gatlin, South Carolina, with his widowed and shut-in father, his superstitious aunt Amarie "Amma" Treadeau, who helped in raising him, and his best friend, Wesley Jefferson "Link" Lincoln. As his return to high school after the summer approaches, Ethan is subject to recurring nightmares, in which he desperately tries to save a mysterious girl. He quickly comes to meet this girl in the flesh: Lena Duchannes, a new arrival to Gatlin, and niece of the infamous town recluse Macon Ravenwood. Though she initially rebuffs his attempts at interacting with her, the pair eventually become friends, despite harassment from other classmates due to the town's distrust of strangers. This excessive hatred escalates until Lena is almost expelled, spearheaded by Link’s mother Mrs. Lincoln.
After many strange events, Lena reveals the truth to Ethan: she and her family are Casters, people who possess magical powers. On Lena's 16th birthday, she will be "claimed" as either a Light or Dark Caster without any choice in the matter, and is terrified of becoming Dark. Macon and Amma, who knows of the Caster world, both discourage the two of spending time together, but the two persist and eventually begin a relationship- despite Ethan suffering dangerous electric shocks when being too physical with her. Ethan also encounters Lena's estranged cousin Ridley, a Dark Caster and a Siren (able to manipulate others to do her will), who seduces Link to get close to the pair.
The pair discovers a locket at the Greenbrier plantation, which induces visions of their ancestors, Genevieve Duchannes and Ethan Carter Wate, who were engaged during the American Civil War. They discover that Genevieve tried to resurrect Ethan Carter Wate using the magical Book of Moons, after the latter was shot and killed by Union soldiers. Genevieve's use of the spell failed, and as payment, the Book of Moons cursed the Duchannes family by removing their choice to become Light and Dark, and deciding for them instead. Ethan and Lena find the Book in Genevieve's grave and study it for ways to prevent Lena from becoming Dark. Furthermore, Lena is continuously spiritually attacked by a Dark Caster, Sarafine, who is revealed to be her mother.
When Lena's birthday finally arrives, Ridley and Link organize a huge party for her, which turns out to be a trap to separate her and Ethan. Ethan is lured away by Ridley, who almost pushes his father to succumb to his depression and commit suicide, but relents due to her newfound compassion for Link. Ethan and Link wade through a Civil War battle reenactment to find Lena, but encounter Sarafine, who had possessed Mrs. Lincoln in order to stoke the town's hate against Lena. Sarafine reveals to the trio that Lena, unlike the rest of her family, has a choice: she can claim herself Light or Dark, but will kill all the Casters in her family of the opposite orientation when she does. They also learn that it is impossible for Casters and Mortals to be physically together, as the shocks would eventually kill Ethan.
During Sarafine's attempts to convince Lena to turn Dark, Macon arrives, but is forced to fight his brother Hunting, an Incubus like him, but who feeds on blood, while Macon chose to spend his life feeding on Mortal thoughts and dreams instead to avoid succumbing to his Dark nature. Ethan escapes, but is stabbed by Sarafine while searching for Lena, and falls to his death. Desperate, Lena unleashes her magic and makes the moon temporarily disappear, seemingly canceling her Claiming and postponing it for another year.
Lena and Amma find Ethan's body, and unable to let him go, use the Book of Moons as Genevieve did to bring him back to life. The spell succeeds, but exchanges Macon's life for Ethan's. Ethan wakes up, unable to remember what happens, and finds Lena grieving over her uncle. The pair mourn together, and the next day, Ethan finds Lena to have one green eye and one gold- respective marks of Light and Dark Casters.
