This article originally appeared in Vulture.

Last year, when David Edelstein and I put together our list of the 25 Greatest Horror Films Since The Shining, we sparked some debate among readers as to whether our choice for No. 1, David Lynch’s Mulholland Drive, was even a horror film. Some readers thought it absolutely belonged; others appreciated that we’d come up with an unorthodox choice; and many others thought that it in no way deserved to be on there. While there was never any real doubt in our own minds, the question itself is worth exploring because it gets to the heart of what we now consider “horror.”

True, Mulholland Drive doesn’t fit into any of today’s typical horror subgenres: It’s not a slasher movie, it’s not a monster flick, and there’s no haunted house. The only zombies, ghosts, or vampires in it are of the metaphorical kind. Nor does Lynch’s film stick to any of those stupid “rules” that Jamie Kennedy’s character expounds upon in Scream. In some cases, it actually upends some of the more common elements of modern horror. (Spoiler alert: The only girl that dies in Mulholland Drive is the final one.)

Of course, rules can be fun to make and break with this sort of thing; that’s why the Scream movies are often quite entertaining. But I daresay that horror is, along with comedy, one of the most subjective and least rule-bound of genres—because it gets to the heart of what an individual viewer finds scary. This is further complicated by the fact that horror often lives alongside another genre—the thriller, usually of the mystery or suspense kind—that is in many senses its fraternal twin. Also looming over the debate is the specter of the “art-horror film,” a genre that Lynch has perfected and made his own, and which I wrote about earlier this year. That’s a subgenre that Mulholland Drive definitely does belong in—though an art-horror film need not necessarily be a horror film (see: Only Lovers Left Alive).

Most people would agree that Mulholland Drive is at the very least a thriller. Is it more than that, though? At the time we wrote the list, David said the following about Lynch’s film: “The movie flirts with being a conventional whodunit. Then—this is what makes it horror—the story line splinters, doubles back on itself, and begins to forge an entirely new set of connections. Roles change. Identities mutate. Things that made no sense make less sense—then, suddenly, more sense.” He puts it well. The film’s story starts off as one thing, and is then totally corrupted and becomes something else—or rather, it becomes many different things. Narrative logic departs and the subconscious, the fantastical, the horrific starts to take over. In many ways, that’s what makes Mulholland Drive so tantalizing to look at in terms of genre: At times it seems to be about the very boundary between horror and thriller.

Let me step back a little. In one of the rare instances when he wrote about aesthetics, Sigmund Freud analyzed tales that “[arouse] dread and creeping horror” and explored the notion of “the uncanny,” which he defined as “that class of the terrifying which leads us back to something long known to us, once very familiar.” Stanley Kubrick reportedly pored over Freud’s famous essay on the uncanny when he and Diane Johnson were developing the screenplay of The Shining, and one can see it in the finished film: The Shining takes things like fairy tales, cartoons, Big Wheels, baseballs, and even parental love, and then weaponizes them.

The uncanny is the realm in which David Lynch regularly operates. Consider the iconic opening scenes of Blue Velvet, in which commonplace images of small-town life—white picket fences, verdant lawns, smiling firemen, happy neighbors—give way to freak accidents and severed ears. Or how the protagonist’s elegantly appointed house in Lost Highway is transformed into a space of gnawing, uncertain terror, thanks to the revelation that someone may be recording him. Or the way Eraserhead takes the notion of domesticity and turns it into an industrial nightmare.

Mulholland Drive, too, is full of such elements. Among the most notable is an early scene at a nondescript, vaguely ’50s-inspired diner that contains the most effective “scare” I’ve ever seen in a movie. Two men sit in a booth, as one, Dan (Patrick Fischler), tells the other about a dream that takes place inside this very same diner. He notes that the other man is in his dream as well, standing near the door and very frightened. Then Dan reveals that he knows the source of their fear. “There’s a man, in back of this place. He’s the one who’s doing it.” He adds, “I hope I never see that face, ever, outside of a dream.” At which point the two of them walk out behind the diner and proceed towards a dumpster. And, well …

This is about as perfect a “horror” scene as one can imagine. The oddly floating camera, the strangely somnambulant delivery of the actors, the way they seem to be literally pulled towards the dumpster, the anticipation of the reveal. And, yes, the sound—that ever-present, Lynchian thrum that infects even the most mundane things with anticipation and dread. The scene also sets up this terrifying thing behind the dumpster—is it a hobo, a demon, or something else?—as being a pivotal figure, even though we only see him briefly a couple more times later in the film. (“He’s the one who’s doing it” is such a delectably vague statement.) So, right at the outset of Mulholland Drive, we have the suggestion of the supernatural and demonic, of something fantastical lurking beneath what seems, at least, at that point, to be a somewhat straightforward thriller.

The ‘50s diner isn’t the only familiar, commonplace thing that Mulholland Drive poisons for us. Consider the popular golden oldie reimagined as a creepy, haunting dirge; or the corny, drawling, old-fashioned cowboy who seems to be either a hit man or a messenger from the beyond, or possibly both. Or look at the way the film plays with Tinseltown clichés the same way that Blue Velvet played with Americana clichés. We have the fresh-faced ingenue (Naomi Watts) who’s just arrived in town (after winning a Jitterbug contest, for crying out loud). We have the hotshot director (Justin Theroux) who’s trying to deal with studio and money-man interference. We have the dark-haired, mysterious femme fatale (Laura Ellen Harring) straight out of film noir. How interesting, too, that so many of these are things from the past. Lynch has often mined the collective imagery of the 1950s—his childhood—for his cinematic visions of the uncanny. Mulholland looks, on the surface, like one of his more contemporary films, but it’s still suffused with the detritus of the earlier era, as if the innocence of the director’s youth is colliding with the bloodcurdling darkness of the world in which he works.

That collision is what Mulholland Drive is actually about (or rather, one of the many things it’s about). In the film’s early scenes, Watts’s character seems the very picture of a naïve, wannabe starlet, all can-do gumption crossed with wide-eyed impressionability. She’s playing a cliché, and Lynch marks her as such through the exaggerated nature of her performance. Similarly, Harring’s performance as the exotic mystery woman is initially so over the top as to be borderline laughable. There’s a reason for all this. Lynch is creating something extremely familiar—too familiar, in fact—the better to toy with and unsettle us. It starts early on, when we see Watts’s character step out of the airport with a friendly elderly couple. After they go their separate ways, we see the couple in the back of their car, their grins still plastered on their faces, now unreal and hideous. When they show up later in the film, after they’ve been unleashed from their box by the devil behind the dumpster, we can’t tell if they’re letting out maniacal cackles or ghoulish screams. Their final reappearance is probably the second most frightened I’ve ever been in a theater.

As Mulholland Drive proceeds, then, this detective story eventually gives way to something far more terrifying. Lynch uses the visual language of horror—handheld shots that appropriate a character’s point of view, for example, or a tendency to isolate his characters in dark frames—to undermine the film’s early scenes of bright-eyed naïveté. Naomi Watts’s nodding-head, wholesome, Nancy Drew mannerisms eventually give way to a figure that’s far more dark-eyed, pale-faced, terrified, and lost—someone for whom the world has become one of disillusionment, anxiety, and terror.

Think of it this way: A mystery often empowers its protagonist; more often than not, they become active in uncovering the truth behind what’s happened. But horror takes that power away. Horror movies are usually not about people seeking the truth but about them being chased, stalked, killed, or haunted. If there’s one thing that defines the genre for me, it’s not so much terror as powerlessness. Horror movies, at least for much of their running times, take away a protagonist’s—and, by extension, our—agency. They make us victims.

And that’s exactly what happens in Mulholland Drive. By the end, it appears that the lead character was investigating her own death all along. Or maybe she was, at the point of her death, reimagining her life as a fairy-tale version of the Hollywood nightmare she found herself in—an extra reinventing herself as a starlet, in sort of a cross between All About Eve and An Occurrence at Owl Creek Bridge. Or maybe she was doing something else entirely. The magic of this film is that it seems to explain itself even as it slips through our fingers. It refuses to let us capture it, which just adds to our unease.

But the film also begins to reflect on itself. As many readers will recall, Mulholland Drive was originally going to be an ABC series, and much of what we’re seeing in the film is Lynch’s pilot episode. But then the network canceled the show, and Lynch shot additional material to turn it into a stand-alone feature film. While I have no idea where the overall plot of Lynch’s intended TV series would have gone, it’s a safe bet to assume that it would have kept working these aforementioned tropes, the way Twin Peaks did with its small-town clichés.

It could be said that when ABC rejected Lynch’s pilot, he got a glimpse of his own powerlessness. It was certainly not his first time: The director has had his share of run-ins with the industry over the years. But on the evidence of some interviews, he was uniquely heartbroken and angry over the abandonment of Mulholland Drive. I can’t help but think that his frustration added to the film’s angry portrayal of the Dream Factory as a place of actual nightmares.

One could argue that without that extra element of bitterness, of real-life disillusionment to mirror the film’s fictional despair, Mulholland Drive would never have truly come into its own. When I asked Lynch about it earlier this year, he told me, in his usual aw-shucks tone, “It was never destined to be a pilot. Whether it started out that way or not, all the things that happened just pointed it more and more toward being a feature.” And amazingly, it seemed that he didn’t have a grand design for the story when it got canceled. “I always say I love the idea of an open-ended story,” he said, “but I’d never gotten to that point where I was seeing scenarios. I liked the idea of the mystery of it. So it became a feature. And it was supposed to become a feature.”

So, where does that leave the genre issue? For the most part, it doesn’t matter. Mulholland Drive is Lynchian—the creation of an artist so unique that his work can in no way be pigeonholed. And Lynch himself would probably not consider it a horror film either; he considers it more of a “love story.” But my own nightmares suggest otherwise; no other film manages to give me bad dreams as consistently as this film does. That’s because, along with its genuinely impressive scares and its expertly mounting sense of dread, Mulholland Drive, like the best horror films, gets at the most unsettling of existential fears—that the world we imagine ourselves living in is an illusion, and that we have no control over our fates.

See also: The 25 Best Horror Movies Since The Shining