As Casey (Elijah Wood) and Delilah (Jordana Brewster) are hidden a closer inside the teacher's lounge, they bare witness to their school nurse being strangled by two of their teachers. As they manage to flee, scared of what may lay ahead if they get caught, they meet the nurse - alive and breathing. They soon notice that all their teachers, and most of their fellow students, seem to be different, and begin to suspect an alien infection. As they gather the few others who seem to be themselves, they find that the most effiecient way to kill these aliens seems to be using one of Zekes (Josh Hartnett) drugs. The only way to get rid of them all now, and potentially save the world, is to go after their Queen..