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

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.

The film never slows down or bores, plunging from one harrowing sequence to the next.

Exactly the movie you think it is, but not the movie you want it to be.