After being homeschooled her entire life and having spent the last twelve years in Africa, 16-year-old Cady Heron begins her first day at North Shore High School. She has trouble making friends and is put down by the teachers on her first day, although she does befriend outcasts Janis Ian and Damian Leigh. Janis and Damian explain the school's various cliques to her, warning her about the "Plastics", a trio of wealthy and mean girls consisting of ruthless queen bee Regina George, insecure gossiper Gretchen Wieners, and bubbly airhead Karen Smith. Regina,Gretchen, and Karen take a shine to Cady and unexpectedly invite her to join the Plastics. Upon realizing this, Janis hatches a plan to infiltrate the group and destroy Regina's reputation.