Renner is Aaron Cross, a black ops agent who suddenly finds himself under attack by his own employers following complications caused by the actions of Jason Bourne. Cross joins forces with Dr. Marta Shearing (Rachel Weisz), also being hunted by the CIA for her connection to the program of which Cross was a part, and together they work to elude their pursuers.
Renner does well in the lead role, looking and acting the part of Aaron Cross whilst at the same time making him a likeable and, at times, sympathetic presence. Weisz is also pleasing as Marta, balancing both the emotional and physical sides of her character well. Edward Norton does well with what he has, although his character - a shady high-ranking CIA operative - feels underdeveloped, never receiving enough screen time to allow the actor to make him truly believable. The same can unfortunately be said for many of the less prominent characters. A key antagonist in the film's final act receives no development whatsoever in fact, coming across far too much like deus ex machina to feel in any way authentic.
The action is enjoyable enough, but it is in this area that it truly becomes clear that The Bourne Legacy is not the same calibre of action film as those in the trilogy preceding it. Having written all four Bourne screenplays, Tony Gilroy clearly knows the series inside out, and he makes this apparent through the intelligent nods and references to events of the previous films (mostly The Bourne Ultimatum) that come up at several points throughout Legacy. Gilroy also directs here, but unfortunately never manages to imbue proceedings with the same energy or panache that Paul Greengrass brought to the previous two installments, or even that of Doug Liman who helmed the original. What Gilroy produces is not awful, just never memorable. I found myself struggling to recall any genuine action highlights that had stuck with me not long after watching.
That's The Bourne Legacy's key problem: it's a Bourne film in name and plot, but not in style or execution. It's a perfectly serviceable action film, flawed but enjoyable. But the fact that it's linked intrinsically to one of the most highly acclaimed series of action films ever made only serves to highlight how ordinary it is. I wouldn't go as far as saying that this is an unnecessary continuation of the series - the nature of this being a "sideways" sequel is one of the most inventive aspects of the film. But to get the most out of The Bourne Legacy, you might be best to emulate the circumstances of Matt Damon's character at the start of The Bourne Identity before watching, and forget everything you know about Bourne.