Joe D'Amato, latter-day king of sleaze, is the guy behind this pornographic reworking of the whole women-in-prison genre, of which I'm sure he made a few entries himself. Sadly, SEX PENITENTIARY is a disappointment for anyone who goes in looking for some semblance of a plot, because this is wall-to-wall sex and nothing else.
The story is about a police raid and a couple of women who are caught up in it and sent to prison. There, the warden is the usual sleazy type, and a couple of other women have plans to escape. That's all in the way of plotting you're going to get, and indeed very little happens other than the straightforward sex from bored-looking performers.