The principal of Opportunity, Alabama's high school finishes her speech, welcoming the entire student body to a new semester and encouraging them to excel and achieve.
The students get up to leave the auditorium for their next class.
The auditorium doors won't open.
Someone starts shooting.
Told over the span of 54 harrowing minutes from four different perspectives, terror reigns as one student's calculated revenge turns into the ultimate game of survival.