Butcher Block is a weekly series celebrating horror’s most extreme films and the minds behind them. Dedicated to graphic gore and splatter, each week will explore the dark, the disturbed, and the depraved in horror, and the blood and guts involved. For the films that use special effects of gore as an art form, and the fans that revel in the carnage, this series is for you.

The word “gamechanger” elicits eye rolls when it’s applied to horror, for good reason. It’s too liberally used, diminishing its meaning. But when it comes to Alexandre Aja’s breakout film, High Tension (Haute Tension), that caught France off guard 15 years ago, it’s difficult to avoid the word. There was a rising trend of brutal films steeped in psychosis, extreme violence and sexuality, but up until that point they’d mostly been arthouse films, like Claire Denis’ Trouble Every Day or Gaspar Noé’s Irréversible. High Tension took it to a new level, placing it squarely in the realm of horror. It ushered forth a new wave of extreme horror in France, made TIME magazine’s list of “10 Most Ridiculously Violent Films,” and introduced a new, ruthless voice in genre filmmaking.

Released 15 years ago in France on June 18, 2003, it made waves months later at the Toronto International Film Festival, where Lionsgate acquired rights for North American distribution. They then had to trim many of the gory, vicious death scenes so that the film could be released with an R-rating; it’s uncut form an easy NC-17. While the controversial final act twist remains a huge point of contention for many, Aja delivers a thrill ride that lives up to its apt title. His brand of bloody horror manages to feel fresh while still paying homage to the classics.

Between Aja and his longtime writing partner Gregory Levasseur, they set the tone early with the introduction of The Killer, a creep in a Citroen H pleasuring himself with a severed head that he discards before driving off to find his next victim. He finds Alex’s family farmhouse, where she and best pal Marie are staying to get some studying done for the weekend. Only Marie is still awake as The Killer ruthlessly slices his way inside, graphically decapitates dad and slits open mom’s throat. Not even Alex’s kid brother is safe- though his death was initially written far more graphically than when they shot it. They realized that perhaps having a little boy’s brains splatter the camera when he’s gunned down might be a bit excessive. From there, the plot becomes an intense cat and mouse game as Marie pursues The Killer and her kidnapped friend, anyone caught in the middle be damned.

Aja’s vision is executed to uncomfortable levels thanks to the fantastic makeup and gore effects. That’s because Giannetto De Rossi is the special makeup effects artist. De Rossi has an impressive, lengthy body of work dating back to the early ‘60s, but he really sharpened his talent for gore and viscera working on many of Lucio Fulci’s gory horror films. Zombi 2, The Beyond, and The House by the Cemetery all feature De Rossi’s makeup effects. That the team also consulted with a coroner on blood spray and trajectory, it’s no wonder why the film’s gore feels so harrowing and gruesome.

One of the most squeamish inducing moments of the film is when Alex gets a massive shard of glass stuck in her foot, severing her Achilles tendon. It’s a well-executed gag that induces sympathy pains, but it’s also an homage to The Hills Have Eyes. Aja pays tribute to The Texas Chain Saw Massacre as well, in the chase sequence involving a circular saw. There’s even an ax to the chest in homage to the first movie that traumatized Aja in his youth, The Shining.

The homages and a remarkable plot similarity to Dean Koontz’s Intensity means that High Tension doesn’t seem to wholly original. Yet Aja’s stylistic choices, his unflinching gaze on horror, and a stunning array of practical gore effects by De Rossi made this film something special. The final destination of High Tension’s narrative doesn’t stand up to the nerve-fraying journey to get there, but it’s such a primitive voyage into extreme cinema that it’s ok. That it helped pave the way for a string of extreme horror to come is even better.