Such a frustrating disappointment

Instead, you get a movie that's enjoyable enough, but leaves you feeling like it could have been much, much more.

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.