Mightygodking.com -- My Inception No-Prize
Interestingly, the scenes without him all feature Ellen Page, whose character is oddly underdeveloped and inconsistent considering how prominent she is. She’s set up heavily (Cobb remarks on how she’s a natural at manipulating dreams), has a heavily symbolic name (Ariadne) and gets a number of scenes without payoffs (for example the scene where she makes her totem, the chess piece.) But in the actual action of the movie she’s not very important, being mostly a vehicle for exposition — the “new guy” that other characters can explain things to, as well as the person who ferrets out Cobb’s backstory. There’s nothing wrong with that, except that there’s another character who plays a similar role — Saito, the one played by Ken Watanabe — and at first glance, at least, the movie would be stronger if he had the role to himself: he has an emotional investment in learning the rules of the game and understanding the plan (since he wants it to succeed) and there’s tension added if he learns about Cobb’s issues with his wife (since he has the power to reunite Cobb with his children), while Ariadne is both uninvested and undermotivated. In fact, her motivation changes several times throughout the movie: at first it’s just professional interest, then a desire to protect the other team members, and then finally (for no clear reason) she’s determined to complete the mission even at the risk of her and Cobb’s lives.
So here’s my attempt at a No-Prize: none of these things are mistakes. The whole movie that we see is a dream, but Cobb isn’t the only real person in it: Ariadne is there too (and maybe Joseph Gordon-Levitt, what the hell.) She has inserted herself into Cobb’s dream because he is still stuck in limbo from his experience with his wife — when he experienced her “dying” that was her waking up, but he’s still asleep. The mission is actually to rescue him; like the fake mission explained to Cillian Murphy in the hotel room, it’s a fiction designed to make him rescue himself. That’s why she plays coy at first — the trick of getting the dreamer to do the work for you — then draws out his emotional issues, and in the end is determined to complete the mission at all cost. It also explains her name: Ariadne, after all, was the one who got Theseus out of the labyrinth.
But why was she so determined? Because Cobb has been dreaming longer than he realizes — ten years or more — which explains another motif with no apparent payoff, the hiding of his children’s faces throughout the movie. Ariadne is his daughter.