From the Wikipedia entry:
The movie centers around Aaron Boone (portrayed by Craig Sheffer), a young man plagued by dreams of a city called Midian, populated by bizarre creatures and deviants of all types who refer to themselves as the "Nightbreed". Aaron is framed for several murders by his psychopathic therapist, subsequently killed by police and resurrected by the magic of Midian. Boone joins forces with the other monsters to defend themselves from the true monsters of the story: humankind.
If you haven't seen it yet, go rent it or borrow it from a friend. After you've seen it and said "WTF?", read the article to find out how you can help get Clive Barker's original vision out to the masses. And, after you've done that, go read the novella if you haven't already.