Hot in theaters and on-demand right now is director Emerald Fennell’s Promising Young Woman. It stars Carey Mulligan as Cassie, a med school dropout who spends her nights enacting revenge against men who try to sexually assault her when she pretends to be stumbling drunk at clubs. Her obsession is born from the experience of her best friend, Nina, who was raped at a party and later killed herself when she was disbelieved. When Nina’s rapist returns to the area as a well-respected doctor who is getting married, Cassie ramps up her quest to finally make him pay.

I really enjoyed this movie and was on the edge of my seat for the entire run time. Mulligan is a captivating presence when it comes to dark circumstances, something she proved when she starred in arguably the most terrifying Doctor Who episode of all time. Her ability to be an almost primal force of vengeance while still coming across as likeable made the movie feel grounded in a way other films are not.

When it was all over, I asked myself, “is this a horror movie?” That’s a really dicey question for a man to ask about a film on this subject. I’ve seen it said that whether you consider it a horror movie depends largely on your gender, meaning that if Cassie seems like a monster that says more about you than it does her character. It’s a very fair take, but I think it’s worth dissecting the horror aspect more deeply.

I didn’t initially think of Promising Young Woman as horror because it has a minimal body count. There is only one death on screen, although it is a doozy that involves an agonizing two minutes worth of smothering someone with a pillow until that person finally stops moving. There are Jason Voorhees machete kills that aren’t as brutal, and one of the more disturbing things I learned writing about serial killers is that the scene is extremely accurate.

Then again, lots of horror movies don’t have high body counts. His House, which was one of Netflix’s best horror films last year, didn’t have any deaths. Neither did their version of Gerald’s Game aside from the heart attack in the beginning. The Shining only has one death, so does Creep. The film that Promising Young Woman reminded me the most of, Amulet, also has just a single death.

The next thing I focused on was the fact that Promising Young Woman isn’t scary. There are no jump scares at all or shots of bloody gore. Cassie does these incredibly shocking transitions from pretend inebriation to calculating attacker, but they’re unsettling instead of spooky. The movie plays with two scenarios where it appears she has crossed the line into monstrous action, though in the end it is shown she has not sunk to the level of the people she wishes to punish.

This is probably why the film is listed as a thriller, a term I hate with a fiery passion. Ever since Silence of the Lambs (which is definitely a horror film in my opinion), thriller has often been code for “horror, but mostly starring women and without monsters.” It’s a weird way that female protagonists in horror get separate treatment. The term isn’t totally without merit. There’s worth in distinguishing something like The Cell from a regular slasher movie, and both from something like Seven, but too often it’s used to weasel movies and books out of the horror genre.

So, if it doesn’t have monsters, isn’t scary, and lacks a massacre, why is it a horror movie? I think it comes down to one word: nightmare. A horror movie is something that would be a nightmare if you dreamed it.

Cassie’s existence is nightmarish. Not only is she locked in a pathological and dangerous game constantly trying to rewrite her friend’s assault and death, but it’s also clearly ruining her life. She’s unhappy, lonely, distant, and incredibly self-destructive. For all that she is still a powerful force and nearly a superhero come the end of the movie, it’s horrifying to watch her do her dance.

As the movie progresses, her need to punish people becomes more and more diabolical until it is clearly going to end in violence and probably murder. When you pull out the scalpel to use on a man handcuffed to the bed, no matter how righteous your cause might be, that’s horror territory.

Genres by nature have nebulous edges. There are not defined borders, and only movies that intentionally start out to be horror films definitely land there. Promising Young Woman obviously didn’t, but that doesn’t exclude it from the horror title. In fact, it would be nice if more films like it were included in horror lists because it’s an excellent film that explores the grotesque in new and interesting ways. Horror is far better for its presence, and that alone is a good reason to claim it.