Fandango describes it briefly, and not by doing it any favors, like this:

Writer/director John August ponders the metaphysical aspects of life and art in an episodic allegory that follows three artists as they embark on a soul searching journey of fate versus free will. When a troubled actor is placed under house arrest in “The Prisoner,” his imagination begins to run wild due to the fact that his spirited publicist and cynical neighbor provide his only link to the outside world. Later, after the planes of reality fold in on themselves during the production of a Project Greenlight-style show which documents the filming of a popular sitcom in “Reality Television,” “Knowing” follows a successful video game designer and his family as they become stranded in the middle of nowhere due to automotive issues. Ryan Reynolds, Hope Davis, and Melissa McCarthy star in a drama that peels back the layers of reality to ask whether or not mankind really has any control over his ultimate fate. ~ Jason Buchanan, All Movie Guide

 The movie is broken down into three completely different parts, requiring the three stars to play completely different roles.  This is where the movie surprised me.  I’m going to have to give props to Ryan Reynolds and Melissa McCarthy. ² Ryan Reynolds has become known for his comedic rom-coms and fluffy comedies and Mellissa McCarthy isn’t even on many people’s radars to be cast as a leading lady.   Both of these actors I have seen in various movies and television shows where I was never unimpressed by them but never really gave them a second thought afterwards either, however in this movie I was actively impressed by both of their acting chops.  

It wasn’t hard to get lost in their performances and forget that it’s the same people playing entirely different roles.  Ryan Reynolds goes from playing a shallow, dense, actor in the first part to giving a layered portrayal of a gay showrunner in the second part and then a completely different performance as a nurturing father in the third.  My words do it no justice, I promise.  There is no way that I can describe Ryan Reynolds change in inflection from character to character or how Melissa McCarthy is able to play herself in one segment without looking like a self-aware tool.    This of course has a lot to do with the script’s characterization and John August’s direction, but there was definitely a reason he cast the way he did.

Though the plot of the film is good, it might not be for everyone, however, it is not difficult to give a solid recommendation on performance alone.  Next time you’re in Blockbuster, rent The Nines.