Trying to bring the Italian giallo genre into the then-popular American slasher genre, Nightmare is a half-clever attempt. Those two extremes don't seem like a good fit, with the typical slash-and-hack, one-by-one structure of the slasher genre mixing a bit awkwardly with the more flamboyant, open-ended and director-focused giallo film movement. "Nightmare" isn't particularly coherent and can feel a bit half-hearted at times, but it has enough startling moments and a truly twisted (and brutal) view of sexuality to at least be interesting beyond it's initial viewing.
Often considered a Grindhouse staple, it shares the qualities of many other films of that "genre": lousy dubbing, horrid acting, completely conspicious continuity blunders, a soundtrack and film print that makes the viewer feel like their head is being held under muddy water. It's also unusually bleak and morally ambiguous for an American film, a telling sign that this was directed by an European. There's also a sense of the American-slasher puritanism, as noticed by the Killer's view of promiscious adults around him, but it's not quite as black-and-white as many of the like-minded films at the time. Largely because we're asked to look at the film's largely unseen killer with a more subjective eye.
"Nightmare" may be poorly made, although a few cat-and-mouse sequences are well-staged and engaging enough, but it's far from useless. It's cross between American DIY ethos and lavish, fetishitistic European flavoring is uneven and sloppy but always weird and alluring enough to keep you watching. The film's modest cult following is understandable.
