Slow pace in the most part of the movie.

It's no definitive masterpiece but it's damn close.

Tells a fascinating and unsettling true story, and does so well, without pretending to have all the answers.

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."