All along, they've been calling this the summer of threes — you know how "they" can be, putting things into tidy little boxes. And they focused mainly on the ballyhooed blockbusters that came out at the beginning of the summer: third installments in the "Spider-Man," "Shrek" and "Pirates of the Caribbean" franchises.

But now as we're creeping into August, traditionally a dumping-ground time at the movies, we have easily the best threequel of all.

"The Bourne Ultimatum" kicks all of their butts — literally and figuratively. Clever and smart, fast and fun, it's the first one that doesn't feel like a dragged-out continuation of a series but rather a climactic, satisfying culmination. (Though, who knows? The ending does leave the door open for the possibility of "Bourne 4.")

Paul Greengrass, who also directed part two, "The Bourne Supremacy," as well as the riveting "United 93," continues to prove himself a master of mood. He's done something astonishing here: He's made an action film that's both delicate and aggressive, a difficult balance to strike.

It's all stuff you've seen before — car chases, fistfights, international jet-setting and spy vs. spy intrigue — but it's so expertly crafted and the cast is so superb that "The Bourne Ultimatum" exceeds all expectations of the genre.

And it's even got a brain in its head, too. The script from Tony Gilroy (who also wrote 2002's "The Bourne Identity" and 2004's "The Bourne Supremacy"), Scott Z. Burns and George Nolfi, offers definite themes on the prevailing mistrust of government, but never gets specific enough that the film will feel dated in a decade.

Matt Damon remains a strong, stoic force in the center as Jason Bourne, the amnesiac CIA assassin of Robert Ludlum's novels, still seeking answers about his hazy past. This time, glimmers of how he became a trained killer are beginning to flash into his memory, which simultaneously makes him more of a threat and puts him in greater danger.

As in the first two "Bourne" films and last year's "The Good Shepherd," Damon has enough subtlety to play an enigmatic figure who still has a soul. Greengrass reportedly told him to be more "butch" and more intense, but he also shows just the right traces of vulnerability to remind you that you're watching a complicated human being, and not just an efficient killing machine. This is especially true in his scenes with returning actresses Julia Stiles as fellow spy Nicky Parsons, who risks not just her job but her life to help him, and Joan Allen as CIA investigator Pamela Landy, who brings class and intelligence to the role of woman who develops sympathy for the person she's targeting.

Starting in Moscow (where he leads authorities on a tense train chase, reminiscent of "The French Connection") Bourne hops to Paris, London, Madrid and eventually New York, seeking details about the super-secret government program that made him who he is today — fellow graduates of which have now been assigned to take him out.

David Strathairn's Noah Vosen, who runs the unit with bloodless arrogance, tries to track him down using impossibly ubiquitous surveillance equipment. But Bourne being Bourne, and possessing an infinite number of passports, he keeps outsmarting him. A scene in London's crowded Waterloo Station, where Bourne meets a journalist (Paddy Considine) who's also looking into the covert program, is a dazzling display of intricately fluid choreography. Greengrass makes it look effortless.

But he cranks up the intensity even higher during a protracted foot chase across apartment rooftops and through narrow stairways in Tangier, which ends with a knock-down, drag-out, furniture-smashing fight between Bourne and another assassin who's come from the same unit and is just as skilled. At one point they are literally trying to destroy each other with anything they can find — washrags, toothbrushes — and what's great is that Greengrass knows he doesn't need to overwhelm the sequence with needless music. The slapping, punching, crashing and cracking provide their own engrossing rhythm.

Later, things get a little ridiculous as Bourne emerges almost without a scratch from what has to be the most gnarly car pile up in the history of New York City, but hey — it's so well staged, it's easy to ignore reality.

Besides, this is summer, the time you want to escape from it all at the movies. Brilliantly, "The Bourne Ultimatum" lets you do that.

"The Bourne Ultimatum," a Universal Pictures release, is rated PG-13 for violence and intense sequences of action. Running time: 110 minutes. Three and a half stars out of four.