A stranger in a metal mask hands out free tickets to a movie screening. A woman puts on a prop mask as a joke and it scratches her face. When the film begins, a man onscreen puts on the same mask and cuts his face the same way.

DEMONS (1985) traps its audience inside the Metropol theatre as a strange infection spreads tooth and claw through the aisles and the doors will not open. Among the trapped are a pair of college students, a pimp named Tony and his girls, and a blind man and his daughter.

Lamberto Bava, son of Mario Bava, directed from a script he wrote with Dario Argento, Franco Ferrini, and Dardano Sacchetti. Argento produced. Claudio Simonetti of Goblin composed the instrumental score, but the rest of the film's soundtrack is pure mid-eighties metal: Billy Idol, Accept, Motley Crue, Saxon.

It became a touchstone of 1980s splatter cinema, a movie about a movie that eats its own audience, practical effects and all.