Sabrina Swanson loved high school. She lived for it - she stills lives for it. But there was one thing she loved more: besting her arch rival Rosario Stewart at any cost. So much so, that when she's tasked with putting on her ten-year reunion, she doesn't just give it her all, she makes it her life's mission to show Rosario up once and for all by throwing the best ten-year union in the history of reunions. Her perfect plans get thwarted, however, when someone digs up and puts on the possessed school mascot costume, the Wallingham Warthog. When Sabrina first realizes the Warthog Monster is roaming the halls in a murderous pursuit, she attempts blissful ignorance in order to keep the party going and her reputation intact. But her silence only causes more bloody chaos, from the beheading of the former-party-girl-turned-religious-zealot to impaling everyone's favorite wheelchair-bound teacher. Sabrina and Rosario reluctantly accept a tenuous truce to work together to defeat the monster. If it falls apart, it's game over for them all.