Seventeen-year-old Millie Kessler (Kathryn Newton) is just trying to survive the bloodthirsty halls of Blissfield High and the cruelty of the popular crowd. But when she becomes the newest target of The Butcher (Vince Vaughn), her town's infamous serial killer, her senior year becomes the least of her worries.

When The Butcher's mystical ancient dagger causes him and Millie to wake up in each other's bodies, Millie learns that she has just 24 hours to get her body back before the switch becomes permanent and she's trapped in the form of a middle-aged maniac forever. The only problem is she now looks like a towering psychopath who's the target of a city-wide manhunt while The Butcher looks like her and has brought his appetite for carnage to Homecoming.

With some help from her friends---ultra-woke Nyla (Celeste O'Connor), ultra-fabulous Joshua (Misha Osherovich) and her crush Booker (Uriah Shelton)---Millie races against the clock to reverse the curse while The Butcher discovers that having a female teen body is the perfect cover for a little Homecoming killing spree.