A brilliant film that helped define a genre

I was totally surprised at how great this film.You could feel your paranoia rise as the film went on and as you gradually learned the details of the real situation.

if their story seems completely bonkers, almost like a feverish work of fiction, you ain't heard nothing yet.

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."