Simple and well acted, it has tension enough to knot the stomach.

In truth, there is barely enough story here to make a film.

Just intense enough to provide a much-needed diversion, just lightweight enough to make you forget about it soon after it’s over. It’s not exactly “good,” per se, but it does what it sets out to do in terms of putting us on edge, which makes it … successful?

One of the most extraordinary films you will see this year. Take that as you want.