I've spent the last two weeks trying to figure out what to make of the depiction of torture in Zero Dark Thirty, even before there was a controversy surrounding that exact same subject, and in two weeks, I have gone through so many first paragraphs without ever getting further to the actual content of the movie than "Jessica Chastain is the lead actress", I can't tell you. In the end, I'm giving up: for the purposes of actually getting the damn thing reviewed, I'm just going pretend that it is a work of fiction with no real-world ramifications at all, and maybe once it has its wide release in January, we can come back to the topic and have a good conversation about. But just for the record: unlike many very smart people and like many other very smart people, I don't think the film is particularly ambivalent about torture - it doesn't celebrate torture, but doesn't doubt for a second that it was useful - and even if it was, ambivalence towards an evil act is no better than endorsing it.

I'd like to say that it took a great deal of sober introspection to decide how that made me feel, but that's exactly the point, that it didn't: the movie had me eating out of the palm of its hand by the ten-minute mark if not earlier, and that is exactly how you can tell that this is terrific filmmaking: it could take a person like myself, whom I would describe as "furiously anti-torture", and for 157 minutes be so exquisitely crafted that I just didn't care, about real-world considerations. Because, as a movie, damn me if Zero Dark Thirty isn't everything it has been hyped to be and more, a feverishly thrilling, decade-spanning CIA procedural that recounts the mechanics involved in finding Osama bin Laden using all the tricks of the spy trade, embodied in the stubborn, slim frame of fictionalised composite Maya (Jessica Chastain), recruited to the agency right out of high school, an intelligence expert of icy composure and no real personality to speak of, until the very last moment we see her in the summer of 2011, when she finally permits herself a reaction to her success - and that reaction is not at all triumphalism, but something much more akin to "I wasn't expecting that. Now what?"

After a lengthy audio montage of phone calls from inside the WTC towers on September 11th, 2001 - the only crippling misjudgment in the film, exploitative and pandering - the movie dumps us right in and never slows: Maya, newly arrived in Afghanistan, is confronted with the CIA's most unsavory intelligence-gathering tools, asked to pitch in a helping hand during a waterboarding session conducted by Dan (Jason Clarke), who will be her most steadfast colleague through the next several years. This rather grueling sequence, shot by director Kathryn Bigelow and DP Greig Fraser (the third and best job of three great jobs of cinematography by that man in 2012) in a much more intimate and interior version of the same juttery, handheld documentary style Bigelow used in The Hurt Locker, is the first of an almost uninterrupted flow of "the CIA at work" scenes, in which Maya goes from a green agent finding her feet, to a hyper-competent specialist, to an intensely focused, almost Ahab-like figure, bent on finding Osama bin Laden, and capturing him or killing him, not for justice, not for revenge, and not for jingoistic bloodlust, but because after a while it's the only thing she knows how to do.

The film might be Bigelow's baby, a far more intense and detailed study of life under pressure than the overdetermined, overrated Hurt Locker, but it's Chastain's triumph: her short career has included great and not-so-great performances, but nothing in the same league as her Maya, an extraordinary, captivating blank space. We are never given a sliver of information about her personal life, and that's in Mark Boal's script; but we never get much about anyone else in the film, including Dan, or Jennifer Ehle's Jessica, or any of the other featured CIA operatives, and in those cases, the actors still create vibrant, living characters; but Chastain does not suggest an inner life for Maya on any level. Which, typing it out, sounds dreadful - far from it! What it gives us is a protagonist who is less a person than a force of will, and since Chastain is very clear choosing to strip Maya clean of personality rather than simply failing to give her one, it actually ends up being an impressive psychological study of an anti-personality; besides which, it results in the devastating final shot of the movie, for which I would not give up anything.

Though it might be The Chastain Show in so many ways, I certainly don't mean to denigrate the very real work Bigelow does in Zero Dark Thirty, and just the fact that the film is two and a half hours long and still flies by recklessly tells us what we need to know about how tightly its director controls the pacing and rhythm of the film. The documentary-style thriller is extremely old at this point, of course, and Bigelow invents no wheels; she merely uses the wheels already available to her to unbelievably good effect, making a film in which every little bit of data that Maya or the rest are able to scrape up through ingenuity or luck feel like the most important thing we've ever seen on screen; a mid-film sequence in which a character makes a series of decisions ending in death becomes one of the best thriller moments in 2012, as we are keyed in that something is amiss, but can't help but want things to turn out as well as the characters do.

The most impressive bit of filmmaking, though, is surely the movie-ending raid on bin Laden's compound, which is already a brave structural gambit - it's the first time we've been separated from Maya's POV, and we leave it for what feels like a good 30 minutes - but is also a terrific mixture of editing, sound design, and sickly green-tinted cinematography that turns a simple action sequence into a horrifying, chaotic "you are there" gesture.

What the film is not, is the unmitigated no-holds-barred Best Thing of 2012, the way the early awards season would have you believe: though it is a thrilling experience, it is almost solely experiential, depicting events and processes without having any particular insight into them, or even an apparent interest in such insight. It's unbelievably solid craftsmanship in the absence of any kind of overriding ideas other than the "cinematic journalism" Boal and Bigelow have been talking about; and while it is very great at that, journalism does not, as a rule, purport to be ageless.