Matt Damon is back as undercover agent Jason Bourne in a new espionage action-adventure based on the best-selling books by Robert Ludlum. Alan Silverman spoke with the stars and filmmaker Paul Greengrass for this look at The Bourne Ultimatum.

Jason Bourne is good at what he does ...deadly good. The trouble is, he is not sure why and not sure who he is. As was explained in the earlier films - 2002's The Bourne Identity and The Bourne Supremacy two years later - he is a highly-trained CIA operative; but the secret program that turned him into an assassin erased his memory. As bits and pieces of it start to resurface, he is now more of a liability than an asset to the his former bosses in the agency.

Of course, Bourne is a product of the best training they could give him; so stopping him is no easy task. As they are trying to kill him, he is trying to shed light on the secret and illegal operation that turned him into a killer.

Matt Damon says playing Bourne again was made easier by the way the story develops as the training-induced amnesia begins to wear off; and, the actor admits, the action can be fun.

Matt Damon in scene from The Bourne Ultimatum

"The whole thing is, in away, this middle-aged fantasy. Okay, I get bonked on the head and I wake up and I speak 12 languages and this really cool German girl falls in love with me so, to a certain extent, it's a little bit of wish fulfillment, but it's a fun role to play," he says.

It also looks like it can be physically punishing as Bourne uses his fists as well as his wits. The dirty little Hollywood secret, according to Damon, is that the exciting fight scenes are some of the most tedious to shoot. "Well, it's very, very technical. It's seven moves or whatever and we just do it over and over again until someone at the monitor would say 'okay, good!' It's just incredibly technical and boring, actually. The fun is when you get a take and it looks really brutal and vicious and (afterward) you are laughing and saying 'oh, it looks great,' but in terms of being challenging mentally, it is not. It's like watching paint dry," says Damon.

Of course, sometimes that paint barely has time to dry in the hyper-thrilling, but also achingly realistic chases through New York, Paris, London and Tangier. Director Paul Greengrass, who also made the second film of the series, The Bourne Supremacy, is better-known for documentaries and films that deal with contemporary social issues, like last year's acclaimed United 93. The English-born film-maker says after that intense dramatization of events on 9/11, he saw The Bourne Ultimatum as a refreshing change.

Paul Greengrass on the set of The Bourne Ultimatum with Matt Damon

"I love doing them and there is a bit of every film maker where you want to 'strut your stuff.' You want to to get out and do the car chase and the fight and the chase," he says. "Also, it's thrilling to connect with a mass audience. I've only ever done it the one time with The Bourne Supremacy."

As much as possible, Greengrass says he takes the film out of what he calls the isolation of the movie set as he puts the action in the middle of real-world locations like the streets of New York or London's Waterloo Station.

"You can't close down Waterloo Station," he explains. "It's the biggest station in London and about 300,000 people go through it an hour. You get problems with that, of course, but what you get to compensate for that is this tremendous rush of energy: the raw energy of life really unfolding around you and it's the same in Waterloo or Tangier or New York. It creates this energized, vibrant, authentic landscape that the real character can move through."

Scene from The Bourne Ultimatum

The Bourne Ultimatum also features David Strathairn as the CIA official who wants to eliminate the problem by eliminating Bourne. Joan Allen, reprises her role from the second film as the dedicated CIA officer who wants to keep Bourne alive; and Julia Stiles is also back as the analyst who becomes Bourne's ally.

"What is interesting about these movies is that they don't deal with good guys and bad guys; it is the choices that those characters make that makes you label them good or bad," Stiles says.

Also in the cast: Albert Finney, Scott Glenn and Paddy Considine. The Bourne Ultimatum was filmed at locations ranging from North Africa to Europe and America.