There is one way in which a person could seriously take issue with the documentary The Imposter: it skirts unnervingly close to exploiting its subject rather than presenting it, and with a subject this sensitive, exploitation is to be particularly avoided. For the movie is, at its heart, about a 13-year-old child who went missing in 1994 and almost certainly died, whether immediately or in the intervening years, it's hard to say.

Note that I say could take issue, not will take issue or ought take issue: for the fact is, despite its borderline-crude approach to a topic of particular delicacy, the movie is never as questionable as all that, but succeeds in being a gripping thriller, heartbreaking family drama, and fascinating true-crime saga all in one package. It's as solid a piece of sheer entertainment as anything else to see release in 2012, while being a compelling human interest story in the bargain, managed by director Bart Layton (whose crime doc bona fides largely consist of executive producing the TV series Locked Up Abroad, which I have not seen, but it sure sounds like it might also wave in the direction of potential exploitation), and if the cost for having it is that it's not the most stringent and morally respectable journalism imaginable, well, worse things happen at sea.

Things get very convoluted very fast, but it starts this way: in '94, Nicholas Barclay had a fight with his mother Beverly Dollarhide, and stormed out of their house in San Antonio, Texas, whereupon he was never seen again. In 1997, a completely unrelated 23-year-old French-Algerian man named Frédéric Bourdin was attempting to evade arrest in Spain, and did what he did best: pretend to be a runaway teenager. No, literally, that was Bourdin's profession, if we can use that word: he pretended to be lost adolescent boys, he claims because he suffered a loveless childhood, and found that he could win attention and affection that way. Pretending, this time, to be an escaped kidnap victim from America, he was connected through a rather dense series of sitcom-level mistakes to Nicholas's name, and in a fit of improvisation that even the latter-day Bourdin doesn't attempt to explain or understand, he elected to agree with this identification.

If it weren't a true story involving a genuine missing child and notionally distraught family members, The Imposter would from this point onward increasingly resemble an ingenious and breathless farce: Nicholas's adult sister, Carey Gibson, flew to Spain to meet her long-lost brother, and upon finding this grown-up man with a French accent, light copper skin, and nut-brown eyes, in contrast to her brother's white skin and piercing ice-blue eyes, immediately recognised him as her own flesh and blood without even cursory hesitation. That was good enough evidence for the government officials involved, and Bourdin was sent back to the States with great enthusiasm, met by Dollarhide with every bit as much blithe candor as by Gibson, and treated as something of a hero by the news media and law enforcement alike, especially after telling the FBI a heated story about a sex slavery ring in which boys were sold into prostitution serving the Spanish military, with their eye color changed using drops. Case officer Nancy Fisher, after initial doubts, ate this all up, and the only person in the entire world who looks to even marginally suspect that this person who resembled Nicholas Barclay in no meaningful way whatsoever might not, in point of fact, be Nicholas Barclay was private investigator Charlie Parker, hired by a TV news magazine to do some background work on the case; he wasn't even assigned to poke holes in the story, and only began doing so on his own initiative upon finding that everybody else failed to notice how ridiculously far-fetched the whole situation was.

First off, it's a hell of a story, populated by a remarkable assortment of broken figures: none more captivating than Bourdin, the very essence of a charming bastard. He agreeably fails to present himself as a lost soul or misunderstood romantic figure or anything but a selfish person who figured out that he could get what he wanted by lying well enough, but even as he tells us this all with such straightforward plainness, it's next to impossible not to be swept up by his commanding ability to spin a story of how cleverly he made all the right choices by the skin of his teeth to make this impossible sequence of events spring to life. He's immensely likable, without our ever forgetting that he's a complete and utter (though long-since redeemed) creep and emotional predator, and maybe worse: at one point, without seeming to notice what she's said, Dollarhide recalls that "Nicholas", having re-entered the world, was striking up a fledgling romance with a girl at school.

In point of fact, Dollarhide, and Gibson say an awful lot of things in their interviews where it doesn't necessarily seem to be the case that they're aware of what's going on (one does try not to be classist, but with the admitted drug use, the poverty, the transparently shitty parenting - Nicholas was a frequent runaway, and had multiple tattoos at thirteen - and the ignorance of simply facts, the family checks almost all of the boxes under the header "white trash"), and this begins to answer the film's endlessly repeated, mind-boggling question: how in the hell did Bourdin get away with this, for even a little while. He certainly doesn't know, and seems disgusted with a world that would permit a slimy sort like him to triumph thus. Parker doesn't, and appears to be simply confused. Fisher doesn't, and seems rather embarrassed by all of it and clearly hopes that she can hide her complicity in the whole mess by talking in very crisp, objective tones. Nicholas's family deals with the question by talking right past it, reliving the days of '97 in richly observational terms that suggest that it's easier to return emotionally to the exact moment of thinking the boy was home safe, than to adopt a perspective from more than a decade later in which they have to confront their actions.

Eventually, Parker and Bourdin independently advance the same theory for how this ludicrous con managed to work, one that Layton rather obviously endorses; it adds a startling wrinkle to a situation that was already nearly ready to burst with wrinkles, and turns the last third of The Imposter into a nail-biting suspense movie of a particularly weird kind. Throughout, it's been an exercise in excellent technique, using dramatic re-enactments with as much pointed force as any documentary I've seen - implicitly, Layton suggests that since the whole story is all about deception and hiding the truth, what's one more layer of fiction provided by actors blending into the stories the interview subjects are telling - but the last sequence is something at an entirely new level, eschewing objective reportage entirely to just yank us around through the magic of editing, a gambit that would be intellectually dishonest in any documentary other than one whose theme is thus hammered home not only verbally but in the movie's own structure: we'd rather have a good, comforting, compelling story than bald-faced facts.

And thus does The Imposter play as a wildly engaging yarn, and as something of a parable about human behavior: how much easier it is for us to tell and believe and live lies, because lies are about choice and control. Every interviewee besides Parker is at some point in a situation where they are happier because of lies than they would be with the truth; and not one of them seems genuinely sorry to have put themselves in that situation. In a film that was less fun to watch, that might seem caustic; but this is immensely fun, a dizzy real-life mystery told with steady but never sobering humanity.