In a small dark room a large drum hangs from a ceiling. In front of the drum stands a chair. A drumstick, attached to the drum and controlled by an electrical mechanism, beats against the taut skin every few seconds. A tiny light at the tip of the drumstick goes on and off regardless of the beat. At the same time, a video image showing a closed mouth in a human face is projected onto the surface of the drum. The image slowly rotates so that the viewer cannot tell which is the upper and which the lower lip.
Every few seconds, at irregular intervals, the mouth opens, revealing the teeth inside, and a scream is heard. Sometimes the scream, the beat of the drumstick and the light occur simultaneously, and sometimes separately.