It’s 1977 and you have a four-post bed that you have to store for the weekend before it goes to the customer. So how can you make money out of this situation? Make a horror movie obviously.
There is a demon that lives in a painting and he somehow kills anyone that sleeps on the bed. That it.
The producers try to make it more arty and creative by changing the location of the bed, the background story of each victim and the way the bed eats the victim. Its all junk. But its a good junk movie.