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.

When it comes to difficult, hard to watch films that elicit uncomfortable reactions to the extreme violence depicted on screen, Gaspar Noe’s Irreversible ranks high on the list. There’s a 10-minute sequence in it so harrowing and bleak that it’s become infamous. So when he had repeatedly named a little seen, banned 1983 Austrian film, Angst, as a major influence on his filmmaking (he’s stated that he’s watched it at least 40 times), you know it’s going to be dark. A film so extreme that it was banned all over the world, even earning an X-rating in France, and the controversy surrounding it contributed to an overwhelming debt that ensured it would be writer/director Gerald Kargl’s first and last film.

It’s likely in large part to Noe’s praises of the film that eventually unearthed Angst from obscurity, and thanks to the great curation of horror streaming service Shudder, horror fans are finally able to see the film that makes even Henry: Portrait of a Serial Killer look somewhat tame. There’s an opening card on Shudder that warns of the ultra-violence that lies ahead, but it becomes quickly forgotten as it introduces the viewer to K. As K. is in the process of being released from prison, his inner monologue narrates his sordid childhood that gives detailed illustration as to how this psychopath was formed. The unconventional camera work and the framework of this narrative makes it easy to see why it’s so ahead of its time, and further makes the viewer forget that K. has depraved violence in store, even when he tells us he’s eager to kill again.

After a botched attempt to make his taxi driver his first victim post-prison release, he flees into the woods and winds up at a seemingly empty, large isolated home. He finds a disabled man inside, whose mother and sister arrive home shortly after. It’s here that this psycho-killer film gets from mildly unsettling to full-blown discomfort, as K. goes after each member with frenzied ferocity.

That Kargl makes K.’s attacks so visceral despite being mostly bloodless is effective. It’s a real-time, intimate look as K. tortures, defiles, and kills his victims. Even still, none of it prepares the viewer for K.’s final kill, so vile, bloody, and steeped in realism that even when the preceding scenes would be enough to earn the film its reputation, this scene alone would do it on its own merit. So much blood spilled, and Kargl used pig’s blood instead of fake blood to perpetuate that since of authenticity. The murder alone feels uncomfortably real, but then K. decides to take it a step further by drinking blood, vomiting, and even necrophilia.

The events of the film are based on true life Austrian serial killer Werner Kniesek. Kargl’s film feels so authentic because it is. Kniesek’s triple homicide ranks among the most ruthless in criminal history, and Angst feels like an intimate portrayal that seeks to understand what drives psycho-killers to kill. Kargl and cinematographer Zbigniew Rybcynski’s camerawork is a marvel on a technical level, but it’s pure, unrelenting anxiety. It’s a perfect example that horror doesn’t always have to spill gallons of blood from opening credits to end to earn its extreme warning. In 1983, Angst was way ahead of its time, and even today there’s still no other home invasion horror quite like it.