During the exciting, turbulent and eventually wayward course of “Green Zone,” Jason Bourne discovers the truth about weapons of mass destruction, then teaches an errant reporter from The Wall Street Journal how to be a good journalist.

In the interests of good journalism it should be said that this new film is a Jason Bourne thriller in spirit and sometimes in form, but not in fact”the character played by Matt Damon, Chief Warrant Officer Roy Miller, is an ostensibly ordinary soldier trying to do his duty. And it should be emphasized that the director, Paul Greengrass, and his cinematographer, Barry Ackroyd (who also shot “The Hurt Locker”) have achieved a surpassing sense of reality in the physical production. This is closer to what the war in Iraq, and the fog of war in Baghdad, must have looked like than anything previously captured in a fiction film.

Mr. Greengrass and his star have collaborated before, of course, with fairly spectacular results””The Bourne Ultimatum,” in 2007, and “The Bourne Supremacy” three years earlier. The difference this time starts with the source material. Instead of an extravagantly stylish adaptation of a Robert Ludlum novel, the director was working from an overheated script by Brian Helgeland that claims”for no reasons evident on screen”to have been inspired by a work of nonfiction, Rajiv Chandrasekaran’s excellent “Imperial Life in the Emerald City: Inside Iraq’s Green Zone.” Miller, suspecting that Saddam Hussein’s WMD’s don’t exist, goes off on his own””off reservation” in military parlance”as a one-man truth squad bent on finding out who’s been lying to whom. For a while “Green Zone” generates genuine excitement, as well as plenty of provocation”a fatuous surrogate for Ahmed Chalabi, a pervasive scorn for American planning”but then goes off its own reservation into a won’t-fly zone of awkward preachments and hapless absurdities.

Some of the latter involve the Journal’s role in reporting the war. A fictional reporter for this paper, Lawrie Dayne (Amy Ryan) has taken Bush administration proconsuls at their word. Weapons of mass destruction exist, she insists in her stories, because highly placed U.S. government sources have been told they do by a highly placed Iraqi government source identified only as Magellan. Miller learns otherwise by tracking down Magellan on his own. The Iraqi, a high-ranking general in Saddam’s army, has told the Americans that the WMD’s were a fiction from the very start, but a double-crossing American intermediary played by Greg Kinnear has lied to Washington as well as to the Baghdad press corps.

“How could someone like you write something like this that isn’t true?” Miller demands of poor Lawrie, who confesses to a cardinal sin”she never even tried to contact Magellan”but finally redeems herself by putting the real story out after Miller gives her a dossier of facts on which she can base it. (”Let’s get it right this time,” the chief warrant officer says encouragingly.)

Still, doesn’t that ring a distant bell, a female reporter for a U.S. newspaper who dutifully promulgated the Bush administration’s line on WMD’s? Yes, but the paper wasn’t The Wall Street Journal, it was the New York Times. On this subject, like so many others, “Green Zone” weakens its claim to authenticity with fictional fudgings. And the weakening works both ways. In a movie being marketed as an action adventure and nothing more, a penchant for speechifying””Do you have any idea what we’ve done here?” Miller asks. “What happens the next time we want people to trust us?””pollutes the wellspring of the genre, which is action unencumbered by real-world meaning.

More’s the pity, since so much of the craftsmanship in “Green Zone” is first-rate. Mr. Damon, as usual, takes charge of his character with understated yet formidable authority. (Miller is in charge of soldiers played by Iraq veterans who are re-enacting their real-life roles.) Mr. Kinnear is intriguingly devious as Poundstone, the American intermediary. Igal Naor is impressively nuanced as Al Rawi, the Iraqi general dubbed Magellan by the Americans. And the director, Mr. Greengrass, stages several action sequences”including Miller chasing Al Rawi through bombed-out Baghdad”that set your heart pounding while your brain defaults to a wait state of happy astonishment.

Yet the film suffers from fuzzy areas that refuse to come into focus. Ms. Ryan seems uncomfortable in her thankless role. The usually superb Brendan Gleeson betrays no enthusiasm for playing Marty Brown, a CIA man who has all the right answers but can’t convince his own government. (”Don’t be naive,” Marty tells Miller at one juncture, even though Miller is preposterously prescient, while a simon-pure operative from Central Intelligence is a case study in naiveté.) And the more frenetic the action becomes, the sillier it seems that Miller should be saving the U.S. from self-deception. “The Hurt Locker” stayed on the reservation by confining itself to suspenseful action and an investigation of a complex character. “Green Zone” comes on as Bourne again and ends up out of bounds.

‘Mother’

An absolutely phenomenal film by the Korean director Bong Joon-ho, “Mother” (in Korean with excellent English subtitles) begins and ends with dance. In the title sequence, a woman who’s neither young nor truly old gyrates mysteriously and abstractedly in the middle of a wheat field. In the coda, she literally prods herself to join young revelers on a bus, a half-seen presence in a surreal frieze. Between those two dances she travels on a journey of obsessive devotion to her 27-year-old son, Do-joon, a young man with an impaired brain”his buddy calls it a “special head””and the face of an angel. (He’s played affectingly, though never sentimentally, by Won Bin.)

What a journey it is, for the unnamed single mother and for us. For the sake of simplicity” though nothing proves simple in the end, not even Do-joon’s mind”let’s say that the narrative operates on twin tracks. It’s a story of maternal love that’s the definition of unswerving, and a whodunit that’s set in motion when the cops throw Do-joon in jail after blaming him for the murder of a local girl whose battered body has been found hanging over a railing on a terrace high above the town. He had followed her for a while from a bar the night before and he admits it, in his addled way, but the flimsy case against him has all the earmarks of a classic setup.