The story concerns an insurance agent and Vietnam veteran who goes on a shooting rampage at a Los Angeles drive-in theater where an aging horror film actor is making a promotional appearance. The character and actions of the killer are patterned after Charles Whitman, the University of Texas sniper. The character of the actor is patterned after Boris Karloff, who in fact plays the part.
Although the film was written and production photography completed in 1967, it was released after the assassinations of Martin Luther King and Robert F. Kennedy and thus had some topical relevance to then-current events. Nevertheless it was not very successful at the box office.
However, Bogdanovich, who appears in the film as a young writer-director (i.e. like Karloff, playing a character very similar to himself in real life) credits it with getting him noticed by the studios, which in turn led to his directing three very successful films in the early 1970's.