After the script was bought, the writers were contractually obligated to deliver a complete rewrite of the script within 30 days. They actually delivered it in 2 weeks by taking time off from work, working late, and working weekends.
Writers John C. Kruize and Michael Jones decided to collaborate on writing a horror script in 1980 while working in the mail room at MGM Pictures. They wrote the script for Night Shadows (which was titled "The Pestilence" at the time) while on their lunch breaks and after work. They finished the script in only a few months.
While Josh and Holly converse in her living room, the shadow of the boom mic can be seen on the wall behind Josh's head extending all the way to the right edge of the screen.