Eight years after an earthquake claimed her father's life, Sam Montgomery (HILARY DUFF) is a high school senior who once believed in fairy tales, but had them dashed by her mean stepmom, Fiona (JENNIFER COOLIDGE), and equally bad step-sisters, Brianna (MADELINE ZIMA) and Gabriella (ANDREA AVERY). Although she has a good friend in Carter (DAN BYRD) and dreams of going to Princeton, Sam isn't happy.
That's not only due to being treated like a slave around her house and at the diner her father once ran, but also because other students, such as Shelby (JULIE GONZALO) and her clique, constantly put her down and Shelby's dreamy but misunderstood boyfriend, Austin (CHAD MICHAEL MURRAY), doesn't even know Sam exists.
Even so, her older diner coworkers, Rhonda (REGINA KING) and Bobby (PAUL RODRIGUEZ), routinely encourage her to pursue her dreams regardless of how others view or treat her. Her hopes are buoyed when she meets her potential Prince Charming first over the Internet and then in costume at the school dance, but she can't get herself to reveal her identity to him even when he turns out to be Austin.
From that point on and as Austin tries to figure out who she is and with Fiona doing everything in her power to ruin the teen's life, Sam must decide what's right for her.