Is it any wonder that sleep has long been a topic for horror? It’s our most exposed and disoriented state. Sleep has been scary on-screen since the 1920s, beginning with German expressionist horror. In The Cabinet of Dr. Caligari, which depicts a brainwashed sleepwalker, or Nosferatu (including Eggers’ 2024 take on it), in which a vampiric villain uses sleep to manipulate as well as attack. Since, sleep has found its way into nearly every subgenre. In supernatural-slasher A Nightmare on Elm Street, Freddy Krueger hunts teenagers down in their dreams, one final threat to the fragility of childhood. In the found footage classic Paranormal Activity, sleep has been difficult for Katie her entire life thanks to a demonic entity tied to her familial history. In films like The Amityville Horror, sleeping and waking states give way to fears about domestic violence. In the Insidious series, the nature of sleep itself is a doorway for any sadistic spirit, and its parallels with mental health struggles and domestic violence culminate in a family rift that explores familial trauma in its latest entry, Insidious: The Red Door.