一群学生被匿名邀请到他们高中地下室的"沟党",结果发现自己被困在那里时,一个流氓学生,寻求报复多年的折磨,把整个校园变成一个自由火区。当学生和教职员工被枪和自制炸药击倒时,一名在交火中被抓获的学校看门人向杀手挑战猫捉老鼠的游戏。但是,当凶手设法穿透加固的地下室时,幸存者面临着一个更加可怕的现实。A group of students are sent anonymous invitations to a 'ditch party' in the basement of their high school, only to find themselves trapped there when a rogue student, seeking revenge for years of torment, turns the entire campus into a free fire zone. As students and faculty members alike are mowed down with guns and homemade explosives, a school janitor caught in the crossfire, challenges the killer to a game of cat and mouse. But when the murderer manages to penetrate the fortified basement, the survivors confront an even more terrifying reality.