It's hard to see any effort in the film. There's no comedy to speak of, no real drama and, worst of all.

Go in cold, and you're likely to emerge with your blood boiling. This has to be seen to be believed.

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.

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