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

The film makes a home in your brain and the only cure is to see it again.

A film with more than the usual spoiler issues. Talking about it in any detail feels akin to handing you a gift-wrapped present and saying, "I hope you like it -- It's a thriller about a diabolical secret experiment."

While it is a pity that the story wasn't told with more visual finesse, this is trivial compared to our real-world problems. It takes a good movie to put that into perspective.