In Perugia, a serial-killer is strangling college students. Inspector Martino is in charge of the investigation and has a black and red scarf as the only lead to be followed. He asks the scarf street vendor Gianni Tomasso if he recalls who might have bought the scarf, but the man tells that he cannot remember. Then Gianni blackmails the killer and becomes his next victim. Meanwhile the college students and girlfriends Jane, Daniela, Katia and Ursula travel to an isolated villa to spend a couple of days together during a break from the art history classes of their professor Franz that has befriended Jane. When Jane twists her ankle, Dr. Roberto is summoned and asks her to rest. The student Stefano Vanzi stalks Daniela since he is obsessed for her. Are the girls in danger in the villa? Who might be the killer?