The plot is pretty straightforward, it has some clever twists but nothing ground breaking. The unshakable tension is impressive, maintaining a genuine feeling of suspense and unease from beginning to end. Sarah Bolger's performance is fantastic, she delivers a very human character that you can really feel is tearing apart at the seams. To move the plot forward, they rely on several overly convenient and unbelievable coincidences, and it kinda takes you out of things sometimes. Otherwise, it's an easy watch, if you consider watching a women go through horrible things for 90 minutes to be easy to watch.