The first thing that comes in mind when you see the synopsis is Totally Killer from last year. Apparently this was written before and its just a coincidence but its impossible to not make the connection.
Set in the early 2000s instead of the 80s, and trying to save a sister she never knew instead of a mom are the differences but the rest is very close.
I personally left high school right around 2003 but in my opinion the movie missed the mark on the time period it try to portray. There is maybe one line that made me smile (mentioning Twitter, Facebook and then MySpace wich had a few great years in the late 2000s but disapeared very fast) but altough they use some stuff wich were still popular at that time like discman or Buffy posters, i never got much of the 2000s vibe. If anything it feels like they trying to portray the late 90s instead.
When it comes to slasher aspects, the movie has very few kills and it almost seem like an afterthought at times. They could had done so much with the mystery killer but it was pretty easy to figure out. The mask once again look pretty similar to Totally Killer and can't say anything was very memorable with this character.
With all of that said, there was other aspect i liked. The whole idea of Lucy (the main character) life pretty much living in the shadow (and dark cloud) of a sister she never knew with parents that could never move on, but then experiencing how it could had been. Bonding with that sister had its moments too.
Im gonna go with a 6 out of 10 because the movie is easy to watch and didn't bored me. But its a movie that would likely get the "not gonna remember it in t-minus 1 day" by Jeremy Jahns.
Certainly worth a watch as its included with your subscription if you enoy this genre. But will not become a cult classic or anything.
