"Q&A" is a cop story about New York's fierce, self-protective clans - blacks, Puerto Ricans, Irish, and Italians - militantly loyal to their kind, in a dark, brutal city at war with itself. With the movies "Serpico" and "Prince of the City," Lumet now completes a trilogy of sprawling urban murals about where we are as a culture - he says, in the stink of huge evils.

His shows a chaos of conflicting interests and cultural hatred in hallways, cop headquarters, bars, and interrogation rooms where police and detectives jab each other with racial epithets, ostensibly just joshing and fun, but Lumet sees deep hatreds a-simmering.

When legendary Irish cop Brennan (Nolte) kills a Hispanic thug and makes it look like self-defense, boss Quinn (O'Neal) calls young assistant D.A. Reilly (Hutton) to conduct a Q&A to get details for the grand jury. Laying it on thick about Irish brethren and New York's finest, Quinn says the incident is cut-and-dried justifiable homicide; he means, "Circle the Irish wagons, and don't screw up." Quinn's point is clear to the viewer, but Reilly is a guileless, honorable character.

Indirectly implicated in payoffs at his old precinct, he's somehow baffled when it emerges that Brennan is no hero, and that Quinn's political ambitions have led him to cover up what Reilly learns is a crime. Layers of dirt and corruption unfold: No one has a clear conscience or record. As ever, we identify with the man who holds onto his values long after other people have lost theirs. Reilly will trace corruption to its roots, and his progress carries the movie, as do his reactions - he's our point of human contact.

In Quinn and Brennan, Reilly meets two villainous extremes - the suave and the rugged. Neither man's conscience slows his interests; they give the movie at least two great performances. As Brennan's belly pours over his belt, we know that under the blob is a heart of stone: Brennan is almost pure hate. The actor doesn't flinch from his character's unsavoriness but gives Brennan monumental brutishness, making him seem utterly indomitable.

Assante as Bobby Texador, a suave Puerto Rican underworld boss involved in Reilly's investigation, has a panther-like sleekness - his body seems coiled, lethal, and muscular under expensive silks which reminds the viewer of the early de Niro's unpredictability.