Hereditary received some of the most passionate reviews at this year’s Sundance film festival – and it’s already scored a cool 100% on Rotten Tomatoes. So, as the kind of person who goes to bed with a Stephen King book in hand (nothing more soothing than a psychopathic axe-killer or a car with murderous intent, eh?), I was intrigued to see what all the fuss was about.

After all, how scary could yet another film about a haunted house really be?

As it turns out, very. Amongst a sea of frightened film reviewers – all pale, when the lights came back up, all clinging onto their arm rests for dear life – I was the one sobbing silent tears of terror and pointedly staring anywhere, everywhere but the screen in front of me. I was the one who couldn’t stop shaking on the train home, cringing miserably every single time a shadow passed over my face. And I was the one who lay sleepless in bed that night, eyes wide, convinced that some nameless horror was going to… well, to put it in the words of my 5-year-old self, was going to “get me”.

Read on (if you dare) for my spoiler-free review of the ‘scariest horror film of all time’:

Hereditary begins, as so many horror films do, with the off-screen death of a reclusive family member: Ellen, mother to Annie (Toni Collette), has passed away from cancer. 

You might assume, then, that the resulting story sees Annie and her family – husband Steve (Gabriel Byrne), teenage son Peter (Alex Wolff) and curiously creepy daughter Charlie (Milly Shapiro) – struggling to come to terms with their grief, as they uncover some strange and dusty skeletons (so to speak) in dear old granny’s closet. That it will be nothing but creaking floorboards, ghostly figures out the corner of your eye, eldritch voices screeching in the darkness and jump-scare upon jump-scare upon jump-scare. That it will be, essentially, the basic haunted house film we all know and love – the kind you chomp popcorn along to, scream at semi-half-heartedly, and laugh with relief when the credits roll at the end.

Wrong!

I cannot stress enough that Hereditary is unlike any horror that’s come before it – and it would do the brilliant writers a great disservice to suggest otherwise. Sure, it starts off being about grief and dead grandmothers and the Graham family’s emotional well-being, but – without giving away too much detail – it quickly becomes something entirely different. And it catches you entirely off-guard when it does so, too, like a deer running out into your headlights on a dark country road. There’s no time to hit the brakes, no time for your brain to change gears, no time to process this new information. All you can do is speed forwards, utterly helpless, into this bats**t crazy fever-dream of a film.

Yes, there are a lot of “what’s that in the corner of the room? A sweater folded over a chair? Something worse? Something truly unspeakable?” moments. Yes, there are strange sounds – sounds which could be as innocent as a dripping tap, or… well, something not so innocent. But Hereditary also employs a plethora of entirely new techniques for sending shivers down audience’s spines, too.

It muddles dreams with hallucinations with reality, so you never quite know what’s what. Each family member betrays themselves, in turn, to be a dangerously unreliable narrator – so much so that it becomes increasingly difficult to trust anyone and everyone. Grief proves to be one of the most frightening phantoms of all, plaguing Annie and her loved ones at every corner. And, after a chance meeting with spiritualist Joan (Ann Dowd), Annie takes part in a séance which unfolds exactly as you might expect, right down to the quavering call of “Are there any spirits present?” – before completely and utterly shattering those expectations, one by one.

Throughout, Hereditary refuses to let you get your bearings: classic horror tropes are held up and then ignored, causing your stomach to churn on a pretty much constant basis. Tiny little moments of beautifully banal ordinariness are interspersed with the nightmarish discord (Annie makes a point of reminding her daughter to take her wet socks off when she tracks in mud from the garden, worrying far more about the damp footprints than whatever it was that lured the child out there in the first place). The film keeps its setting fascinatingly indeterminate, too: yes, there are mobile phones – but the teens ride bikes everywhere (which, thanks to Stranger Things, shoots you straight back in time to the Eighties). Yes, there are cars and electric lights – but the furniture is dated, the clothing kept deliberately “classic” or timeless. The teens are seen attending lessons in a classroom which wouldn’t look out of place in Saved By The Bell, the roads stretch out – empty and desolate – like something out of 1969’s Easy Rider, and don’t even get me started on that creepy Dracula-esque house. 

This refusal to commit to a decade keeps you feeling confused, off-kilter and unbalanced. And, as such, Hereditary renders you far more susceptible to the emotions being played out by the overwhelmingly talented actors on screen before you. 

All of the above, though, is merely foreplay (for want of a better word). This overwhelmingly complex film teases, taunts, keeps you on the brink of losing your mind, makes you feel dizzyingly sick with trepidation – so much so that, when Hereditary’s full terrors are unleashed, it honestly feels like something deep inside you has snapped. Irreparably. It is no exaggeration to say that I entered into a strange disassociative state: I didn’t even realise I was crying until I reached up and touched my wet face. 

And things did not get better when the film ended, either. It was as if Hereditary was a parasite that had burrowed itself deep into my brain, latching on to my innermost self and depositing eggs all over it. And you know what’s worse? Those eggs will remain there, dormant, ready to hatch open the next time I’m alone in the dark.

Or, just maybe, the next time I’m not quite as alone as I think I am…

Hereditary opens everywhere on 15 June. Go see it, if you dare.