Riffing on a notorious real-life Finnish multiple murder still unsolved almost six decades later, “Lake Bodom” is not so much a slasher film as a meta-slasher film, toying knowingly with genre conventions and touchstones. This handsomely crafted horror thriller doesn’t get as referential as something like “The Cabin in the Woods,” but it’s similarly inclined to pull the rug out from under its premise at midpoint, then spring additional surprises that are clever if not (for those inclined to scrutinize) necessarily credible. It’s a promising step toward an international audience for director/co-scenarist Taneli Mustonen, whose popular but lowbrow “Reunion” comedies were less export-friendly.

In June 1960, four young campers — two 15-year-old girls and their 18-year-old boyfriends — were found several hours after a brutal attack on the shore of the titular lake, outside Espoo. Three had been stabbed and bludgeoned to death; a fourth was left battered and traumatized, with no clear recollection of the attack. For years, police questioned numerous suspects (including, decades later, the surviving boy), but no one was convicted. The case retains an almost mythic fascination in Finnish culture.

So it’s not entirely unlikely that more than half a century later, our fictional protagonists should head to Lake Bodom in order to reconstruct the circumstances of the crime, and perhaps finally determine its perpetrator. Actually, that’s the agenda for only dweeby, bespectacled Atte (Santeri Helinheimo Mantyla), who’s somewhat obsessed with the murders. His reluctant (and perhaps only) friend, tattooed bad-boy Elias (Mikael Gabriel), is an adolescent horndog with different, predictable priorities. They’ve coaxed female besties Ida (Nelly Hirst-Gee) and Nora (Mimosa Willamo) into coming along. Ida is a baby-faced blonde naif desperate to escape her joyless home life under a fanatically religious patriarch, while the caustic, tomboyish Nora seems most interested in spending time with Ida.

After the girls realize they’re not heading to a cabin as promised — instead, like the original quartet, they’ll sleep in a tent on the lakefront — the high-schoolers get a little high and break into platonic pairs. A late-night bathroom break isolates them further from each other, and at this half-hour juncture the initial violence occurs.

Within 15 panicked minutes, the original tragedy has been all-too-fatally reenacted, to a degree, although whether the killer is an unseen intruder or one of the current party is a question answered by the film’s first significant upending of expectations. There’s another such fate awaiting the guilty parties, however, resulting in a hectic third act that carries echoes of “Wolf Creek,” recent Sundance breakout “Killing Ground,” and other screen tales of nocturnal road peril. (The film’s most slavish homage occurs in flashback, with a locker-room tracking shot that tips its hat to the shot near the start of DePalma’s “Carrie.”)

The twists in “Lake Bodom” are unpredictable enough that one can reasonably suspend the disbelief its increasing reliance on horror tropes requires. (Still, not everyone will feel charitable toward the most outrageous of them.) The screenplay by Mustonen and Aleksi Hyvarinen dexterously welds together conceits not usually seen in a single horror narrative, though their facility can’t fully hide the underlying pulp cliches — nor do the writers perhaps want to.

In any case, Mustonen’s direction lends the enterprise considerable confidence and panache. This is a very good-looking film — Daniel Lindholm’s widescreen lensing particularly excels at eerie forest nightscapes and frequent sweeping aerial shots — paced with cruelly playful precision. Panu Aaltio’s impressive score moves beyond initial ’80s direct-to-video-horror synth cheese to more glacial Tangerine Dream-like sounds and other offbeat complements.