Welcome to a world where chilling nightmares become reality. When you lie down to sleep at night, your body starts to relax but your mind remains aware and can merely watch as you lose all ability to control your motionless body in the darkened bedroom. Suddenly, the door opens and something intangible creeps toward the bed until the hairs on your neck stand on end. You feel a growing anxiety from the evil that slowly begins to take shape. Welcome to the world of sleep paralysis, a state between waking and sleeping that countless individuals experience every day. Even if they don’t know each other, many of these people have the same experience, the same terrifying spectral visits. This chillingly realistic film, one of this year’s Sundance sensations, works with the tools of the horror genre but at its core it remains a pure documentary about a phenomenon for which scientists have yet to find a satisfactory explanation.