When small town high school student Jennifer (Megan Fox) is possessed by a hungry demon, she transitions from being "high school evil"—gorgeous (and doesn't she know it), stuck up and ultra-attitudinal—to the real deal: evil/evil. The glittering beauty becomes a pale and sickly creature jonesing for a meaty snack, and guys who never stood a chance with the heartless babe, take on new luster in the light of Jennifer's insatiable appetite.

Meanwhile, Jennifer's lifelong best friend Needy (Amanda Seyfried), long relegated to living in Jennifer's shadow, must step-up to protect the town's young men, including her nerdy boyfriend Chip (Johnny Simmons).