Valerie Marsh and her three closest friends - Tara, Amber, and Kat - have just started their senior year of high school. Tara's a straight-A student with an Ivy League school in her future, Kat's the lead in every play performed at Riverbank High, and Amber is a popular cheerleader with boys lining up to date her. Valerie, meanwhile, has mediocre grades, works the light booth while Kat's onstage, and has never even gone on a date with a boy. When Tara gets a boyfriend and convinces Valerie to ask her neighbor Lucas out on a double-date, things quickly go awry, leaving Valerie to wonder who exactly she is and where she fits in amongst her friends and peers. Enter Lindsay Walker, an outgoing British bombshell who switches places with Tara's sister Kara as part of an exchange student program offered by their schools. She quickly upstages Tara in front of her family, competes with Kat for the lead role in the winter play, and becomes just as popular as Amber, if not more. But even as tension grows between Lindsay and all of Valerie's friends, Valerie and Lindsay grow closer, and Valerie finds her world turned completely upside down as she struggles to answer questions about herself she'd never been brave enough to ask before.