While not nearly as directly influential as The Texas Chainsaw Massacre (released on the same day), Bob Clark’s 1974 movie Black Christmas is considered by many to be the original slasher film—and they might be right. Ripping countless pages out of its cinematic book, John Carpenter’s 1978 classic Halloween may have become the blueprint of the slasher genre, sparking the deluge of copycats in the late ’70s to mid ’80s, but Clark’s film laid the groundwork first.

Black Christmas is set around Christmas time, but much like Halloween and its own titular holiday, it never becomes immersed in any of the ethos. However, unlike Carpenter’s film, this one allows the spirit of its respective season to inform its every mood and aesthetic—even if not directly.

We follow a group of sorority sisters who receive threatening phone calls at their sorority house, eventually getting stalked and murdered by a mysterious man one by one. We see each murder happen from the first-person point of view of the killer. His first victim, Clare (Lynne Griffin), meets her fate early on, and the first half of the film is spent on the girls and the police looking for her. Phone calls keep coming in, but only the audience knows that Clare’s body is, in fact, up in the attic with the killer himself.

Director Bob Clark unfolds the plot slowly throughout the film but ramps up the intensity during the second half and earns each and every one of his scares wholeheartedly. He doesn’t directly focus as much on the killer himself, which may seem like a weakness at first as we don’t ever get a sound motive—or even an anti-motive for that matter—but upon further analysis and repeated viewings, the killer’s background does become more obvious and we can put the puzzle pieces together.

In one of the B-plots, the film presents a touchy subject matter as fuel for the narrative but avoids any controversy by not giving an explicit opinion one way or another. If anything, Clark even uses some audience members’ view on the topic to his advantage in manipulating them, and our characters, into having an idea who the killer is.

Prior to watching this for the first time, I had always assumed Black Christmas was just another low budget horror film along the lines of Friday the 13th, but the way this movie avoids common exploitation traits, along with the quality of its cinematography and acting, easily proves its artistic worth. Favoring effective suspense and well-earned scares over easy crowd-pleasers, Clark continuously captures each and every chilling moment, ultimately giving us one of the scariest and mind-numbingly unsettling slashers we’ll ever see. Despite being the progenitor for countless films for decades to come, these now-familiar tropes are still somehow executed better here than I’ve seen in any of the movies that have had the time to study and perfect them.

Matching the authentically uneasy tone of the film, the haunting and well-timed musical score by Carl Zittrer is never utilized to fabricate suspense when it’s not there or to make us jump independently of the actual movie itself.

Hauntingly shot and brilliantly concluded, Black Christmas is the rare ’70s horror film that still gets in your head and makes you want to sleep with your lights on as an adult, despite how jaded modern slashers have made us. Clark gets the absolute most out of every scare—such as a simple eye peering through a crack in the door—and provides us with clean cut, yet graphic images that we won’t forget for a long time.