good back-story, and good acting

It's funny, it's tense, it features two great performances from two actors and the director expertly creates a web of odd tension where you actually don't know what is happening for the majority of the run time.

A great movie, one of the best of this year. There was a bit of confusion at one point in the plot, but nothing serious.

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