This is the film's first villain:
And here's villain number two:
A fluffy orderly who is hypnotized by his delusional mother into slicing up eyeballs on living victims. Oh, and this is also part of a movie that is being watched by these two girls:
And the film unfolds as a series of jumps from eyeball-murder film (pleasingly titled The Mommy) to the "real" events of the theater, where murder also starts to happen. This feels like an art film or at least an ambitious film, but you could sort out the structure and plot in a few sentences, as I have just proven.
Mostly, I think I'm not that impressed because other films top Anguish at what it's attempting to do. For movie-in-a-movie stuff, I'd opt for Demons over this. As for the (sub)text of real violence contra horror-movie violence, it's laughable to think this nips at the heels of Targets.
That's not to say that Anguish doesn't have charms. I loved Zelda Rubenstein as the psycho mom and Michael Lerner is fantastic as the killer orderly. The film is shot very competently and the screen/real life stuff is staged well. One small scene, in which a girl pleads for help regarding the theater murder, is just great. "I've got an appointment!" says the guy, brushing her off.
As stated, though, lots of people regard this as a lost classic of sorts, so you should probably not take my word for it and instead judge for yourself.