Jo Mitchell is an 18-year-old high school senior from Ohio. On her first day at North Shore High School, she encounters a clique called "The Plastics": the self-proclaimed leader, Mandi Weatherly; the ditzy girl with the raging libido, Chastity Meyer; and the Hypochondriasis Hope Plotkin. Jo also meets Abby Hanover, whom Mandi perceives to be a rival. Jo becomes attracted to Tyler Adams. Despite Jo's attempts to avoid the Plastics, conflict develops between them and Abby.