There’s a movie you might want to consider watching around Halloween,to satiate your desire for fear-inducing entertainment. Except it’s not a horror flick—it’s a documentary.

The movie in question is called The Nightmare, and it explores the often overlooked sleep phenomenon called sleep paralysis. It affects almost one in ten people on the planet.

The documentary is the work of Rodney Ascher, who interviews people who suffer from sleep paralysis, a condition that leaves a person feeling like they’re awake but unable to move. On top of that, those same people often experience hallucinations that feel extremely real and terrifying.

The Nightmare

The Nightmare

Using actors and special effects, the documentary recreates the dream experiences people who have experienced sleep paralysis. And if the intended effect is to terrify the viewer, then it seems as though Ascher has pulled it off. The film has everything from demonic creatures stalking their paralyzed prey to mysterious figures who lurk in dark corners.

We suggest you don’t watch this one alone. And, whatever you do, definitely don’t watch it right before bed.