The story concerns a quiet insurance agent / Vietnam veteran, played by Tim O'Kelly, who murders his young wife, his mother and a grocery delivery boy at home and then initiates an afternoon shooting rampage from atop a Los Angeles area oil refinery. Several motorists and passengers are wounded or killed on the nearby freeway. When the police respond and start to close in on him he flees and resumes his shootings at a Reseda drive-in theater where an aging horror film icon is making a final promotional appearance before retirement.
The character and actions of the killer are patterned after Charles Whitman, the University of Texas sniper. The character of actor Byron Orlok, named after Max Schreck's vampire Count Orlok in 1922's Nosferatu, is patterned after Boris Karloff himself, who in fact plays the part in his last appearance in a major American film (although Bogdanovich states that, unlike Orlok, Karloff was not embittered with the movie business and did not wish to retire).
In the film's finale, which takes place at a drive-in theater, Karloff — the old-fashioned, traditional screen monster who always obeyed the rules — confronts the new, realistic, nihilistic late-1960s monster in the shape of a clean-cut, unassuming multiple murderer. He slaps the murderer into submission and the police arrive and affect an arrest. The murderer wonders aloud about the exact number of victims after his wounding or killing of several theater patrons,