Jack Terry (John Travolta) is a sound technician who works in horror B movies, providing screams and others sound effects. One night, while he is recording sounds in a park, he witnesses an accident in which a car falls in a nearby lake after a blowout. Jack dives and inside the submerged car he founds the governor of Pennsylvania, dead, and a young prostitute named Sally (Nancy Allen), half drowned. The car accident seems only an unlucky casualty (complicated by the potential scandal). However, analyzing the audiotape he was recording at the park, Jack discovers that a gunshot preceded the blowout and understands that the incident has been a murder. Jack (cooperating with Sally) starts a dangerous quest for truth, while the psychotic hit man Burke (John Lithgow) is occupied to cover the conspiracy behind the assassination.