Mona, a married woman in an unneeded wheelchair, is a bit of a hypochondriac. One day while down in the basement, she sees two of the people in her building having sexual intercourse together. She hides from view, but in the process is electrocuted. When she recovers she finds her head filled with voices, which she eventually recognizes as the thoughts of the other residents of the building.
The building Mona lives in is being sold out from under the residents to a company named KM Enterprises, and many of the residents are for the sale. Mona uses her newfound ability to blackmail the other people of the building into opposing the sale. Unfortunately, the manner in which Mona blackmails them leads them to distrust one another even more, making existing tensions between them even worse. Eventually the tension causes a large confrontation between the blackmailed residents, who wind up killing each other.
During the confrontation, Mona is electrocuted again; when she comes to she finds the voices have ceased. She returns to her apartment and is greeted by her husband, but before she can speak to him the voices return, louder and stronger than ever. As she flails in distress her husband explains that he is the sole owner of KM Enterprises, and also reveals what "KM" stands for: Kill Mona. Despairing and overwhelmed by the voices, Mona leaps out her upper story window to her death. Her husband then calmly turns off the stereo, halting the tape of overlapping voices Mona had been hearing.