Betrayed is a novel that is part of the House of Night series by mother and daughter authors P.C. Cast and Kristin Cast. The story follows the main character, Zoey Redbird, as she lives and attends school at the House of Night to undergo the Change from a fledgling to a vampyre. Zoey Redbird is the new leader of the social group at the House of Night, the Dark Daughters and Sons. Zoey is also the only fledgling that carries the Mark, which is a tattoo Zoey earns from saving the life of her human ex-boyfriend, Heath Luck.

As Zoey prepares for her first ritual as the new leader of the Dark Daughters and Sons, football players from the local high start to go missing. Zoey knows the boys from her previous relationship with Heath. One by one, the kidnapped murders turn up as murder victims. The boys die of numerous lacerations, bite marks, and loss of blood. Zoey believes someone is murdering the boys, but trying to make it look as if they are vampyre attacks.

While Zoey is trying to figure out who is murdering the boys, she also has apprehension about her mentor, who is also the High Priestess or principal of the House of Night, Neferet. While Neferet is supposed to help guide Zoey through the process of turning into a vampyre, it seems as if Neferet is somehow involved in betraying Zoey. As Zoey continues to investigate the kidnappings and murders, she ties Neferet to recent fledglings that have died during the change, but seem to be wandering the courtyard of the House of Night when the rest of the students are asleep.

After Zoey's roommate and best friend, Stevie Rae Johnson, dies of the Change, Zoey sees Stevie Rae in the courtyard. Zoey realizes Neferet has something to do with changing the dead fledglings into evil creatures. The same evil creatures are responsible for the kidnappings and murders of the high school boys. When her ex-boyfriend Heat goes missing, Zoey has a vision, which leads her to Heath and the underground world where the evil creatures are living. Zoey saves Heath's life, but vows to bring down Neferet at the right time for her part in the murders of the boy and what Neferet is doing to create evil creatures.