I just got back from San Juan, Puerto Rico and on the flight home, I got a chance to watch Inception one more time. I'm sure the last thing the world needs is another interpretation of Christopher Nolan's film, but here's one you might not have heard. WARNING: The follow paragraphs contain spoilers.
I started thinking about totems. Every person going into the dream world has a totem that supposedly only themselves have touched. Except Cobb. Cobb's totem is the same as his wife Mal's, a small top. That got me thinking. There are three people who touch the top: Saito, Mal and Cobb.
We learn later in the film that Cobb and Mal both worked as extractors together and began playing with the idea of a dream inside a dream. From Cobb's story, we know they spent almost 50 years in limbo together before Cobb incepted Mal with the idea that they were in a dream.
Now back in the real world, Mal is still obsessed with the idea that the two of them are still dreaming. Cobb tries to reason with her, using the children as proof, but it is no use.
And now the twist. What if Mal was right? Maybe they were dreaming. How can Mal convince Cobb that it was all a dream? She has to use the one thing Cobb believes is real, the children. What Mal does is create a scenario where Cobb can't be with the children. She kills herself and pins it on him.
Enter Saito. He has chosen Cobb for his special task in part due to the test missions performed in the beginning of the film. But we never see that start of those missions. I believe that Mal and Saito are working together to wake Cobb up from the dream.
In fact, you know from the very first dream sequence where Cobb and Arthur are trying to convince Saito to give them is secret. Mal tells Saito what Cobb is up to, forcing the dream to collapse. In fact, anytime Cobb attempts to go deeper into the dream levels, Mal is there to try to stop him.
What we see at the end of the movie is the failure of Mal to get Cobb to wake up. Cobb is completely lost in his dream world because he no longer believes Mal is real, and she was his last link to reality.
And there we have it. Re-watch the movie and look for the connection between Saito, Mal and Cobb. Also look for clues that Mal was right and that they were living in a dream world when she committed suicide. It's interesting that after a full year, Inception still has the ability to make you think.