If ever any month was made for horror movies, it’s October. Building up to Halloween, there’s a whole month’s worth of movie-watching to fill, whether with hallowed favourites, creepy new additions to the genre or the perennial raft of spooky remakes and sequels that hits during the month.

Yearly rituals are always in need of new blood, however, making October a prime month for unearthing forgotten frights from cinematic history. Dutch director George Sluizer’s 1988 movie The Vanishing (or Spoorloos) is one such under-remembered masterpiece of horror filmmaking. Released thirty years ago this year, The Vanishing’s memory has perhaps been blighted by the wholly inferior American remake that Sluizer himself directed in 1993, which was sapped of all its original potency by Hollywood’s demand for a happy ending. Widely regarded to have one of the scariest endings in cinematic history – Stanley Kubrick said it was the most terrifying film he’d ever seen – the original Vanishing is a horror film with a difference. Entirely free of the sensationalism that was then (and is now) a stock feature of most horror films, The Vanishing tells the story of one woman’s strange disappearance and the consuming effect that mystery has on her bereft partner in strikingly clinical tones that make both villains and victims of the audience.

Young Dutch couple Saskia (Johanna Ter Steege) and Rex (Gene Bervoets) are taking a road trip to their vacation spot in France when, after stopping to stretch their legs at a highway rest stop, Saskia vanishes. Her disappearance is so swift and leaves so few clues that Rex is initially more dumbfounded than he is scared. That effect persists three years later, as Rex lives in perpetual pursuit of any morsel of information that will shed light on Saskia’s disappearance to the detriment of his new relationship: he plasters posters bearing her image everywhere, travels back and forth to France to hunt for clues, and fronts TV appeals assuring her kidnapper that his need to know what happened to Saskia is greater than his need for revenge; the truth is all he asks.

Where The Vanishing marks itself out is in its readiness to share most of that truth with its audience from the outset. Even before Saskia goes missing, we’re introduced to her kidnapper, a mild-mannered French family man named Raymond (Bernard-Pierre Donnadieu). We see him as he spies the couple at the rest stop, strapping his arm into a fake sling; later, we flash back to learn that he feigns this injury to make his unsuspecting young female victims soft with sympathy for him. Sluizer also shows us Raymond meticulously practising his means of abduction, timing himself as he rehearses his lines, pressing chloroform-soaked handkerchiefs to his own face, and measuring his heart rate once the deed is done. Barely a third of the way into The Vanishing, Sluizer has answered for us the central question of stories like this: whodunit?

What he withholds is the why and the how. Raymond gives us the answer to the former himself, satisfying for us the other essential hunger we have when watching films like this: the need to make sense of the psychology of killers.

Raymond himself is not entirely interesting, a fact Sluizer’s detached style of filmmaking accentuates: the scenes in which he rehearses his tactics, for example, are shot in such a matter-of-fact tone that his constant line fluffing becomes more farcical than it does frightening. But Sluizer gives this rather banal villain an edge in a flash back to his childhood. Without spoiling the specifics, they reveal a mind consumed not by homicidal rage but by an obstinate attitude towards destiny; a tenacious commitment to doing whatever it is that he believes he has been predestined not to. There is a quasi-logic to his argument here that makes it more terrifying than most other twisted rationales murderous characters offer up.

That certainly makes Raymond an intriguing psychological case study, but the most effective of director Sluizer’s weapons lies in arousing in his audience an increasingly urgent curiosity as to the how of Saskia’s disappearance. We know who, we know why, but – aside from the inkling the chloroform montage gives us – we don’t know exactly what happened when she left Rex to buy them both a drink. That ignorance is the first that we share with Rex, who, three years on from his girlfriend’s kidnapping, is willing to do anything to learn the truth.

Rex’s curiosity is put to the ultimate test when Raymond, moved by Rex’s TV appeal, agrees to reveal all on one condition: Rex must learn what happened to Saskia by going through the same experience she did. Rex’s readiness to give in to that ultimatum is understandable, given his desperation; for the last three years, he’s been haunted by the ghost of what happened that day, and this is his only chance to exorcise those demons.

What’s more remarkable, however, is that Sluizer makes us, the audience, contradict our own natural sympathies with Rex by willing him on in this incredibly risky gamble. Part of what makes so many horror movies engaging is that they turn us into active participants; wise, wary counsels who sense every danger and know just how to conquer them. Who can watch Psycho, for example, without feeling the salvational urge to reach through the screen and convince Marion Crane to pick another — any other — motel? In The Vanishing, Sluizer intelligently reorients the horror so that, because we’re in the dark with Rex, we make the irrational choice in spite of our own premonitions. He whets our appetite for revelation with the who and the why, but these are mere teasers; hooks to get us hungry for the last of Raymond’s secrets. Just like it does for Rex, sating that curiosity becomes paramount for us, and we’re ready to defy our better impulses to slake that thirst.

Sluizer, who achieved little commercial success after this film, deserves much of the credit for this feat of audience manipulation. His direction adds layers and mood where other filmmakers may have let the film run on the fumes of the plot’s innate intrigue. Much of the movie’s intelligence becomes apparent on re-watching – Sluizer leaves clues for us everywhere – but there are moments that stand out even on first view; Sluizer’s choice to keep Raymond visible, but always out of focus, in the background of one of Rex’s many returns to France, months before he knows Raymond’s identity, is one. It’s difficult to purge your brain of the abject panic induced by The Vanishing’s tunnel scene, too, the total darkness of which has us lose our bearings in time and space (and not for the only time; when we’re plunged into darkness again, Bervoets’ performance becomes a bare bulb of brilliance illuminating us in our shared guilt).

There are further touches of the surreal – such as the moment Rex’s extremely ‘80s computer manifests his persisting obsession with Saskia – but The Vanishing’s commitment to realism is what leaves the biggest impression. Donnadieu all but embodies the banality of evil, while Ter Steege’s charisma is so natural you question why she didn’t go on to bigger things (although she very nearly did, having been cast as the lead in Kubrick’s cancelled Wartime Lies). And by some miracle, Sluizer makes even the dullest of locations — a road tunnel, a highway rest stop — evocative venues for terror. Perhaps they work so well in this respect because they’re transitory in nature; places we should only pass through, never stay, lest we tempt fate. It would spoil the film’s magic to delve too deep into its ending, but suffice it to say that The Vanishing wants us to believe that curiosity works the same way.