Sixteen-year-old Jean "Jinx" Honeychurch, the descendant of a witch, must leave Iowa to live with relatives in Manhattan after the first spell she casts goes awry, but she will have to improve her skills to stop her cousin from practicing black magic that endangers them and the boy they both like.

High school sophomore Princess Mia records in her diary her struggles with geometry, the expectations of being a college student's girlfriend, running for president of the student council, and a potential ecological disaster in her native land, Genovia.