 In Iowa, while dating in a car parked nearby a river, the Theta Sorority pledge Lori Sorenson and her boyfriend hear a sharp noise on the body and top of the car. When the boy leaves the car to see what is happening, he is attacked by an invisible being and killed. Dean and Sam decide to investigate the phenomenon in their hunting trip and arrive in the University of Iowa. When Lori s roommate is also attacked and murdered, the brothers realize that they have to face the evil and moralist Hook Man.