When Edward Norton signs on to play the bad guy in a movie, it's a safe bet he won't just be playing a simple, easily-defined black-and-white villain.

That's doubly true when he's joining the "Bourne" series that has become one of the few reliable alternatives to Bond for fans of smart popcorn spy movies.  The latest entry, "The Bourne Legacy," is an attempt to extend the life of the series past the departure of Matt Damon, who has been the star of the first three films.  My review will be up later this week, but it's safe to say the new film absolutely feels like part of the same world and the same narrative, and Eric Byer, the shadowy government figure who Norton plays in the film, is a perfect addition to the roster of middle-management government types who have peopled these films so far.

Norton is rarely just a gun for hire, instead signing on to films as a serious collaborator, someone who's going to want to dig into the text and see what can be done to elevate the material every single time.  It's an approach that might make some people hesitate, but the filmmakers who embrace the approach tend to get great work from him, and it sounds like Tony Gilroy was absolutely up for the back-and-forth.

What's interesting about the new film is how they seem to have reached this point where it's hard to call anyone in the film a "good guy" or a "bad guy."  Gilroy created very clear motivations for everyone, and certainly we follow Renner's character, Aaron Cross, as he attempts to stay alive when the plug is pulled on the program that created him.  But Byer's not some monster who looks forward to killing anyone.  He is part of this shadowy world of espionage and high-tech, where secrets are currency and where the ends justify the means.  As a result, this is a film about the way secrets are kept and the price of keeping them, and it expands the world of the series without closing the door on any of the options they have for the future.  It's also interesting to see a film like this where the main antagonist doesn't play any scenes with the protagonist except for a flashback.

I certainly hope "The Bourne Legacy" does well enough for this same crew to come back and make another one because I feel like there are plenty of questions left after this film, and because it's not really over until Aaron Cross ends up face to face with Eric Byer.

"The Bourne Legacy" opens everywhere on Friday.