Cutting between various chilling anecdotes of sinister late night visions and horrifying reenactments, The Nightmare manages a tricky balance of visceral fright and sincere investigation. It's a rare non-fiction achievement that earns the ability to freak you out.

As in Rodney Ascher's previous film, Room 237, the subject of obsession is complemented by a despairing attempt to process it, corral it, and somehow conquer it.

More frightening (yet strangely entertaining) than most of today’s narrative horror films.

With The Nightmare, Ascher abandons the strictures of a conventional documentary to frolic in the terrifying netherworlds of human consciousness. It’s not enough for Ascher, a sufferer himself, to tell his audience about sleep paralysis—they have to feel it, too.

The human brain, this movie suggests, is the ultimate horror-movie director, and sleep-paralysis hallucinations are just an extreme form of the standard-issue nightmares we all unwillingly create on a regular basis. It’s one thing to be tormented. It’s another thing to face the grim reality that you’re tormenting yourself.