The first thing that grabbed me about the movie was it's overall style, in the trailers it looks like seeing the main duo as children is just part of the preface but instead the events of them as kids are actually spliced between scenes of them as young adults throughout the whole movie. It's hard to describe but based on the context when the kids show up it's always kind of fuzzy as to whats actually going on, it seems like the two main characters Kaylie and Tim (played by Karren Gillain and Brenton Thwaites) are just re-experiencing old memories but the movie likes to throw curves at you and constantly change the elements of the situation so that you never really no what's going on until it ends.
The plot of the movie is that after their parent's horrific death's as children Kaylie is picking up Tim from a mental hospital more than 10 years later and is convinced that the mirror their dad purchased when they moved into a new house all those years ago was the cause of the events that occurred and that they need to kill it because they made a promise to one another before they were separated. This is the first thing the movie does right , they make it very clear that Tim has been recovering in a stable environment and that Kaylie has been driven somewhat insane being mostly on her own. It keeps you on your toes through the first half of the movie as it keeps changing your gears for you based on who's the focus of the scene.
The second major thing the movie does right is the brilliance of the mirror itself, at least on a conceptual level. They never give a concrete reason as to why but the basic premise is that the mirror is evil and feeds on people Kaylie gathers up all this data of similar deaths that happen when the mirror is brought into a new place and honestly I could imagine that anyone watching the movie could believe she's right or that she's crazy because of the way Tim keeps interjecting. It really does a lovely job of balancing itself . When things do start to get a bit hairy the actual abilities of the mirror start to take shape, all it really does is mess with your perception and feed off negative memories and emotions. Thinking about it it spends most of the movie trying to distract the characters of make them hurt themselves, in a lesser movie it would keep doing more and more and get really stupid but the filmmakers and actors (both of the older and younger Kaylie and Tim) really keep you at the edge of your seat as you try to piece together what's really going on in a movie that moves too fast. Sometimes too fast for it's own good.
Like I said above the only real complaint I can make about this movie is the length, it's barely an hour and a half and while I'm not saying every movie needs to be a 4 and a half hour trek through Middle Earth the movie occasionally feels short on time, and waves over some moments that could build more suspense. Frankly speaking that's really not much of a complaint, I mean there's a character who exists just to die but for the most part the movie is just so clever and so off the wall I would gladly put this in my top 10 favorite horror movies of all time. Go and watch it..but then maybe don't drive yourself home. Mirrors are scary and shit.