Mercy Black was released without warning earlier this week by the streaming giant and is based upon a true story about how two 12-year-old girls stabbed a young girl in the hope of appeasing a malevolent spirit.
Daniella Pineda - you might remember her from The Originals or the latest Jurassic World film - plays a woman who is released from a secure psychiatric hospital years after she stabbed up a young child at the behest of a mysterious demon, the aforementioned Mercy Black.
That's the bit that is based in reality.
You might have heard of the internet urban legend of Slenderman. He's often depicted as a shadowy, tall figure in pictures that circulated on the internet some years back.
In 2014 two girls - Anissa Weier and Morgan Geyser - stabbed another girl 19 times and then claimed that they did so to impress Slenderman, and that he'd harm their families if they didn't do it.
Needless to say, they were locked up for long sentences after being found to have been insane.
In the new movie, Pineda's character Marina tries to return to a normal life following her lengthy time institutionalised. She moves in with her sister and nephew, but things soon start to get weird.
Weird appears to be an understatement. So far, people who have watched it have described it as 'creepy AF' and 'nerve-wracking throughout'.
Good, that's the point of a scary film.
One fan said that it was a 'well-acted, effectively frightening spin on the whole Slenderman premise'.
Another added that it was a 'really creepy movie with an awesome ending'.
The film is directed by Owen Egerton, a director and writer with credits on projects called things like Blood Fest and The Axe Murders of Villisca. He knows his way around the genre, then.
However, in an interview with The Austin Chronicle he said that the film is less about the Slenderman story, and much more complex than that.
He said: "We're not retelling that story.
"We are exploring similar situations, and you want to be - not just sensitive, but respectful of the people involved in those stories."
"Those stories where someone is victim and responsible party, that scares me, and the way I deal with it is to write about the things that scare me."
It's available on Netflix right now, if you fancy a decent scare.
Featured Image Credit: Blumhouse/Universal