The random violence of life in Rio de Janeiro's teeming shanty towns is the subject of director Jose Padilha's bone-jarring action drama. Seen from the viewpoint of the "elite squad" BOPE, the paramilitary police unit which is up against drug-trafficking militias as well as corrupt cops, it's a controversial glimpse of a social abyss. Forget The Dark Knight's Gotham City, these "favelas" are genuinely a world without rules.
Self-mythologising themselves as an authoritarian elite, they wear chic black uniforms and sport the sinister death's head insignia as a badge of honour.
We could be talking about Hitler's SS...but we are not. These are the privileged warriors of BOPE - Brazil's State Police Special Operations Battalion.
Director Jose Padilha, who made the impressive drama-doc Bus 174, views the lawless otherworld that is Rio's slum favelas through the careworn eyes of BOPE Captain Nascimento (Moura).
It's a tough tour of duty. Drug-running gangsters fearlessly swagger across their home turf armed with police-issue guns, cockily confident they will never be brought to book.
Purportedly charged with the task of taking them down, Rio's underpaid and poorly-trained police are pre-occupied with their own scams, ranging from selling engines from their own patrol cars to protection rackets targetting local businesses.
Rising above this murderous, moral-free quagmire is Nascimento...but's he's served his time and is keen to groom a successor, allowing him a life with his wife and newborn son.
Thanks to a pirated DVD, Padilha's grim chronicle of Rio's slumlife - which was scripted by City of God's Braulio Mantovani - has apparently been seen by more than eleven million Brazilians and was the country's top-grossing domestic film in 2007.
That's a bit of a worry. Because there's an extremely thin line between an obsessive attention to detail and salaciously revelling in an unaccountable paramilitary force who operate a blatant shoot-to-kill policy.
Basically, the conclusion to be drawn is that the cops on the ground can't be trusted so the only way to deal with the smack-dealing scum is to tacitly allow BOPE to be judge and jury.
What emerges is not a criticism of a team of uniformed killers allowed to function outside the law but a testosterone-fuelled appreciation of their camaraderie, lethal notoriety and rigorous training methods.
It's a bit like a Latin American episode of The Bill written by Richard Littlejohn and directed by Chuck Norris.