Starting out with a voice-over interview with a former intern of the Ulster County Asylum, we quickly find out that things were not right. "The asylum was built on fear" says the doctor, presumably because a dance academies and hotels had been built over all of the gateways. He tells of an inbred, backwoods drunkard, Joe (William Sanderson), who has been taken to the asylum for the apparent grisly murder of his his family. He was found by the local loud-mouthed sheriff (Tom Savini) holding the bloody skull of one of his kin and mumbling "I sleep, I wake with bad things".
Quickly Eischel discovers that Joe's growth is an infestation of a creature beyond human comprehension named Amducious that is free to gruesomely slaughter humans as soon as Joe goes to sleep, or as Joe says "we sleep, Amducious come, make us free." This leads Eischel down a bloody path to know more, experience more and ultimately free Amducious from Joe's body.
On the one hand the filmmakers try to filch bits of inspiration from Stuart Gordon's RE-ANIMATOR (1985) and FROM BEYOND (1986), particularly in the final act which sports the bulk of the movie's effects work. On the other hand, it still works well for this level of moviemaking, though it seems in a bit of a sharp contrast with the plot-heavy first hour.
CHILL (2007) or BEYOND DUNWICH HORROR (2007) first, then you will really appreciate BEYOND THE WALL OF SLEEP.