early 80s movie with mentally challenged man in basement kills house guests

American horror thriller movie from 1983.

In 1972, the patients and doctors at Stephens Sanitarium were brutally murdered. Over forty years later, the only known survivor returns only to find the ghosts of the past have not been resting in peace.

A young psychiatric nurse goes to work at a lonesome asylum following a murder. There, she experiences varying degrees of torment from the patients.

Trapped inside a fortified home owned by a mysterious couple, a young boy quickly learns the true nature of the homicidal inhabitants, and secret creatures hidden deep within the walls.

An eccentric Youtuber is granted access to film in a house that was previously the scene of a bizarre murder.

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.

A seemingly innocent man is abducted by a notorious L.A. serial killer, who forces his victims to switch roles with him so that he can enact his own capture, torture and murder.

A female college student who started a part-time job taking care of a bedridden elderly person notices an eerie cry from the basement.

Five teenagers frantically run for refuge down into a basement. They barricade themselves inside as they are being hunted down by an insane killer upstairs. The killer’s motive is unknown and the teenagers question why this is happening to them. With the killer holding vigil at the basement door, the teenagers soon realize they’re trapped, as the only way out is the very same way they got in. As events unfold, questions of their own sanity come to light and reality becomes distorted.