Cady Heron is a 16-year-old girl who was previously homeschooled in Africa by her zoologist parents. Upon moving back the the U. S., they decide she should have the chance to attend public school with her peers. Poor Cady has no experience with the catty high school cliques she encounters, and is fairly clueless about fashion. Out-of-place Cady is befriended by outsiders Janis and Damian. Having previously been hurt by the Plastics, an exlusive group of popular (and mean) girls at school, Janis and Damian form a plot to infiltrate the group and humiliate their leader Regina. They send Cady into their midst and the Plastics adopt her. Over time, Cady finds herself turning into one of the "mean girls" herself and because of the cattiness she's let herself get corrupted by, causes a big mess that only a return to her true self can correct.