I’ve been a fan of the “Bourne” espionage movie trilogy for a long time…both the original Robert Ludlum novels and the Matt Damon films loosely derived from the books. Even Eric Van Lustbader’s authorized sequels to Ludlum’s works – flimsier though they may be – are entertaining enough.

When I first heard the title of this fourth film installment, I expected it to be a direct adaptation of the Van Lustbader novel bearing the same name. The book, “The Bourne Legacy,” follows the ongoing adventures of a retired Jason Bourne as he fights to protect his family. I was naturally surprised to find that the “Bourne Legacy” film would center on a new character, Aaron Cross (Jeremy Renner, last seen as Hawkeye in “The Avengers”).

Overlapping with the conclusion of “The Bourne Ultimatum,” “Legacy” follows Cross’ battle to survive a top-to-bottom purge of the U.S. black ops program. With Jason Bourne’s story leaking out to the media, high-level coordinators plan to eradicated all incriminating loose ends.

But Cross is more than just a highly trained super-spy: he’s undergone genetic therapy designed to increase both stamina and intelligence. Dependent on a number of drugs to sustain his augmentations, Cross must locate a fresh supply of meds. Assisting him is Dr. Marta Shearing (Rachel Weisz), an innocent biochemist caught in the crossfire.

It’s a major change from the international espionage and intrigue of its predecessors – and unfortunately, the shift doesn’t work particularly well.

First, the good: if this film was anything other than a “Bourne” movie, it would’ve been pretty strong. The cinematography is well-executed, the acting is top-notch, and the action scenes (particularly a climactic car chase) are still the gold standard for their genre.

The drugs/sci-fi angle, however, feels jarringly out of place. The “Bourne” franchise has always been grounded in reality, and the idea of genetically enhanced warriors doesn’t fit well with that milieu. Since this conflict serves as the backbone of the film, it’s hard to separate these elements from the rest of the movie.

Essentially, “The Bourne Legacy” feels like it was first conceptualized as a standalone work…and only later fitted with the external trappings of a “Bourne” sequel. The ties to the original trilogy feel tenuous at best – particularly the eleventh-hour introduction of yet another covert government program. There’s no holistic integration of “Legacy” into the rest of the series, and it never really justifies its own existence. A fourth film, honestly, was never necessary.

Frustratingly, there seem to be some interesting elements beneath the surface of this film. The very idea of black ops programs raises a host of ethical issues – to what extent, for example, may moral principles be overridden by individuals acting in the service of the state – but these aren’t developed. It’s never quite clear what nefarious deeds are being suppressed…and, in turn, why the government is so desperate to eliminate Cross. This critical omission robs the film of much of its narrative heft.

Some relatively simple fixes could’ve gone a long way toward improving this movie. For starters, too much exposition is provided up front, which robs the audience of the joy of solving the mystery. A bit of reshuffling – moving some scenes around and expunging others entirely – could’ve created a tauter, more intense product. “The Bourne Legacy,” as it stands, doesn’t feel quite polished; I found myself wondering if it’d been pushed into an accelerated release by studio executives.

All that being said, however, this is still an entertaining summer movie. It’s nowhere near the excellence of its predecessors, but it’s a serviceable adventure with plenty of flair. The action is still great, the storyline is engaging enough, and there’s visual style to spare.

If only it hadn’t called itself a “Bourne” sequel…

VERDICT: 6.5/10
An unfortunately pedestrian fourth installment in an otherwise outstanding series.

Normalized Score: 2.4