She's cute. She's loyal. She's psychotic. And, unfortunately for college freshman Sara (Minka Kelly) she's THE ROOMMATE. When Sara arrives at school, she finds new romance with Stephen (Cam Gigandet) and forms a fast friendship with her roommate Rebecca (Leighton Meester). What begins as camaraderie soon turns creepy, and Sara comes face-to-face with the terrifying realization that her new best friend is obsessive, unbalanced... and maybe even a killer!