Three naïve guys, in their 20s, drive from Illinois to LA. A sleazy real-estate agent gives them a great deal on a house in the Hollywood Hills. The night they arrive, a solitary Mexican, who speaks only Spanish, tries to warn them that the place is possessed by Satan. They don't understand him, move in, and plan a party after they meet Lucy, their gorgeous neighbor from down the hill. An old friend of theirs, studying to be a priest, joins them. In the basement is a portal to Hell, so at the party, guests meet their end in various ways. Lucy and her friends may not be who the lads think. Is there any hope for these innocents? Maybe their neutered dog can help.

In a medical school, the freshmen students Alison Blanchard, Brian Cross, Carlos Aclar and Rick O'Connor receive the cadaver of a young woman for dissection in their anatomy class of Professor Walter Blackwell. The atheist Alison has a weird sensation that the spirit of the corpse is trying to communicate with her and tries to unravel who the woman was. Meanwhile, all the persons that handle the corpse mysteriously die.

The night before a local haunted house opens for Halloween, six friends sneak in for a few hours of fun. Soon after entering, they find themselves trapped inside with no way out. Their evening of fun rapidly turns into their worst nightmare as they begin to die and disappear in the most freakish of manners. With every effort to escape blocked, the survivors find themselves being driven deeper into the carnivalesque world of terror. Unable to tell what is real and what is counterfeit, they must trust one another, even if it kills them.