Buffy (Kristy Swanson) is informed that she is the Chosen One, (the one person in her generation who must fight evil and more specifically vampires) by her Watcher, Merrick (Donald Sutherland). She takes this stride - balancing training montages with cheerleading montages. She takes time to develop a romance with the uncool but studly Oliver (Luke Perry) and becomes more self aware, though just as annoying.
Master vampire Lothos (Rutger Hauer) is gunning for her however, and while not menacing her with a broken violin, he manages to kill Merrick. Buffy kills his henchman Amilyn (Paul Reubens) before killing Lothos as well - at the prom in front of all the cool kids who abandoned her when she became distracted by her calling.
Oliver and Buffy drive off into the night on his motorcycle and all those who love the series that would follow, feel Joss Whedon's pain to see his concept so cruelly blundered.
Watch for a bit part by Ben Affleck and Hillary Swank in her first film role.
Thanks Mary C!