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

While it doesn't offer any answers, it both thrills and makes you think.

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?

Strong acting helps the film overcome an uncertain premise and create characters that hold our attention absolutely.