From the opening moments of "Q&A," filmmaker Sidney Lumet leaves no doubt as to the nature of homicide detective Mike Brennan. As the film begins, Brennan cold-bloodedly murders a "suspect" who drunkenly exits a club in a rundown part of town. He then coerces two eyewitnesses into lying so they'll testify the victim had a gun in his hand.

For Brennan it's just another night on the beat, taking care of business his own way.

Meanwhile, young hotshot assistant district attorney Al Riley is assigned to the case — his first. The police commissioner tells him it's a "cut and dried" case of justifiable homicide, and at first that's how it seems. But Riley's investigation turns up some ugly business, and it looks like the corruption doesn't stop with Brennan.

Nick Nolte gets top billing here as Brennan, and he's put on extra weight and his worst slovenly look to play sleaze as only he can. But the story actually concentrates more on Riley, played by Timothy Hutton. Riley is a former policeman whose father was a well-respected top cop. He's idealistic and naive, the perfect patsy for a coverup job.

Riley also has a serious flaw in his character: A sense of subtle racism, which tripped him up some years earlier in his relationship with a woman he loved whose father was black.

Writer-director Lumet is in familiar territory here, having previously filmed two true stories of New York police corruption ("Serpico," "Prince of the City") and touched on the subject of racism from time to time in several films, primarily "The Pawnbroker" and "Dog Day Afternoon." (There are times when this film resembles "Serpico" meets "The Godfather.")

As is sometimes his wont, Lumet here takes a talky and somewhat stagy ensemble approach, which at times makes the movie seem more like a TV miniseries with its weaving plotlines and wandering narrative.

The language is very harsh, heavy with profanity and vulgarity and filled with racial epithets. The latter are, at first, offered playfully between the ethnically mixed members of the police force, but later take on a rage all their own. The violence is quick and unsubtle, though not as grotesque or exploitive as we often see on the screen today. And the messages are mostly heavy-handed in their delivery.

The result is definitely a mixed bag.

There are superb performances by all concerned: Hutton's bewildered innocent, forced to grow up the hard way, and yet managing in the end to still take a rather unrealistic, romanticized view of life; Nolte's unrelentingly vicious vigilante cop, putting his own pride, his askew sense of right and wrong and his all-encompassing desire for self-preservation above all else; Armand Assante as a high-rolling drug-dealer who's smarter than anyone thinks; Wendell Pierce as Hutton's mentor; Patrick O'Neal as the smarmy police commissioner; and many others.

But on the whole this is a sprawling 2-hours-plus terrifying look at the underbelly of New York's legal system with a rather gloomy view of the world. Lumet has given the city a dingy, harsh look as far from Woody Allen's "valentine" view as possible.

Further, he builds a tension between each character, with people wary of their best friends and most respected colleagues. No one is ever really sure who or how much to trust. This may be accurate in context, but it's not very pleasant viewing.

"Q&A" is a movie to respect and admire, but enjoy is probably not the right word. We're familiar with its world and its ethics, and when Lumet soft-pedals his messages his film is quite effective. But more often he's very heavy-handed, and some of the power is lost.

Still, "Q&A" is worth a look as a serious film by an uncompromising filmmaker.

It is rated R for constant profanity and vulgarity, several scenes of graphic violence, as well as some scenes with sex, drugs and nudity.