Sidney Lumet’s police movie, Q&A is an epic portrait of an urban-bureaucratic nightmare. It’s about a criminal-justice system so saturated with cronyism and rancor that it’s beginning to strangle itself. Nick Nolte gives a performance of enormous brilliance as Mike Brennan, a treacherous NYPD rogue at the heart of a homicide cover-up. The movie has flaws, but it’s a complex vision of urban racism and corruption — Lumet’s darkest, most labyrinthine drama yet. A-