Fantastic movie. This review is long, but does NOT contain any spoilers.
The synopsis above is 2 too many sentences long. Trust the story, and the audience. One of the things that makes this film so good is how well it pulls the viewer into the experience as it unfolds.
When a plot is described by stating the aspect that makes it scary (no matter how obvious), the entire movie becomes about the ending.
And what's the point of watching a movie just to see how it ends?
Despite my criticism of the synopsis given, this movie is a super good watch...all the way through.