I have this personal, explanatory theory that all (but as soon as I say “all” I know that counterexamples will present themselves) horror can be described in terms of doors that shouldn’t be opened. This is a bit metaphorical—I think what I’m really keying off of is a sense of transgression—but the “door” as trope in horror media seems common and apt. The horror of the hallway full of closed doors in The Shining (Stanley Kubrick, 1980), the door that the Lament Configuration opens in Hellraiser (Clive Barker, 1987), the trapdoor that opens into a torture chamber in Martyrs (Pascal Laugier, 2008), the very different trapdoor in The Evil Dead (Sam Raimi, 1981).
There’s something about doors as markers of containment: we stand outside, while the truth about the way the world works waits within (that truth, in a Lovecraftian sense, might be the uncaring nature of the universe, or, in a Stephen King sense, might be that monsters are real but that we can fight back). I had mostly forgotten about this doorway metaphor until my recent watch of Saint Maud (Rose Glass, 2019). Think of the hallway that Maud (Morfydd Clark) descends into, before one of her revelatory experiences (you can watch the scene here), and the way that the hallway seems to twist reality itself as Maud barrels down it. (Also think of A Quiet Place Part II (John Krasinski, 2021) and the ways that sealed doors come to play such an important role, endangering the family unit in one sense, protecting it another.)

In Dracula (Tod Browning, 1931), Renfield (Dwight Frye) is marked from the opening scenes in the castle by a kind of persistent, we might say unwise, threshold crossing. Himself a Londoner abroad in Transylvania, we see our first glimpse of Dracula-as-bat when Renfield sticks himself half out the carriage window, attempting to speak to the driver. Then, Renfield faces (in what seems like a legitimate character moment) the decision to enter the castle through both 1) the gargantuan, eerily creaky door, and 2) by having to cut down the cobwebs that Dracula (Bela Lugosi) passes through without damaging. Finally, when he is overtaken by Dracula’s trance, it occurs on the threshold of a doorway leading outside, denoting his in-betweenness, one foot in the world of the vampire, one foot pulling him back toward humanity. (Later, we might note, Renfield’s madness is in part marked by insides and outsides—when we first hear his mad laughter, he remains in the ship’s hold while we look down on him from the outside. Much later, in Dr. Seward’s (Herbert Bunston) office, we see only Renfield’s shadow, our perspective shifted to viewing him on the outside, while we are now on the inside.)

In Let the Right One In (Tomas Alfredson, 2008), Eli’s (Lina Leandersson) outsider status is distinctly marked by her inability to enter places without permission, which we see when she asks, in multiple moments, both Oskar (Kåre Hedebrant) and Håkan (Per Ragnar) to let her in (c.f. the title). But the two moments I’d mainly like to point out are slightly different: the events in Eli’s “crypt” and the moment she shares with Oskar through the glass door. In the former, Lacke (Peter Carlberg) has to jimmy the lock of the bathroom door in order to let himself inside; whenever we’re outside (what I’ll continue calling the crypt), the door to the room remains dead center of frame, emphasizing its importance. This is the moment we see Eli at her most vulnerable, asleep in her pseudo-coffin (another door Lacke has to open). By crossing over the threshold into the crypt, Lacke effectively commits himself to death, opening the door that shouldn’t have been (notably, Oskar never crosses this threshold). Earlier, when Oskar first visits Eli in her apartment, she closes a glass door between them before he can penetrate any further. It is through this door that Oskar finally asks Eli outright if she’s a vampire, and where she admits that she has “been twelve for a long time” (1:20:02). Then, she lets Oskar inside in an inversion of the human/vampire relationship.
I don’t want to pretend that the aesthetic of doors or doorways provides a perfect heuristic into every horror film, but it does seem to be something recurrent that I now can’t unsee. I’ve only watched 2.5 episodes of Mike Flanagan’s new Midnight Mass (2021), but doorways and (even more for this series, at least so far) windows as threshold markers are already featuring prominently. Minor Spoiler for the second episode here, but, near the end of episode two, Bowl (John C. MacDonald) does that thing we wish people in horror movies wouldn’t do: a door creaks open, and he goes right to it, walks inside, gets eaten (although he’s kind of an asshat, so we don’t really care).
Maybe the opening door trope is so appetizing to horror filmmakers precisely because of what the open door represents to all of us — the opportunity for knowledge, even if that knowledge might come at a horrible price.
And maybe I’ll check in again with more about doorways and windows after I’ve finished Midnight Mass.
Much of this post was originally written for a class called “Reading Horror” at Cornell.