BAD BOYS ARE BACK IN TOWN.

Byline: David Kronke TV Critic

AS GOOD AS its first season was for the cast and crew of FX's bad- cop/worse-cop series ``The Shield,'' it was equally bad for the show's characters and the city of Los Angeles.

Vic Mackey (Emmy winner Michael Chiklis) got away with a lot of corrupt behavior, but now he must cope with his wife's disappearance. Other characters saw their principles compromised beyond the breaking point, and L.A.'s police department wasn't helped much by the fact that no one really seemed to question the show's verisimilitude.

Things don't get much better as season two opens tonight. Vic has hired an investigator to track down his wife, but discovers one of his colleagues has disastrously invested their illegal ``retirement fund'' on some poisoned drugs, sending them on a dangerous, surreptitious mission into Tijuana. Dutch (Jay Karnes), in his zeal to put away a drug lord, recklessly endangers a young girl. Meanwhile, in the wake of several scandals, a civilian auditor (Lucinda Jenney) is scouring the barn in search of corruption - Vic and company would probably lay odds on how long it'll take her to unearth something, except they're too busy trying to keep it all buried.

Next week, Vic and Claudette (CCH Pounder) tangle over the same case - Vic's trying to protect the very sources Claudette wants to uncover - and Danny (Catherine Dent) shoots a man from the Middle East in self-defense, provoking what promises to be a torturously difficult Internal Affairs investigation.

``The Shield'' seeks the best of both worlds - combining luridly violent and sexual storytelling with smart characterizations and dialogue and a provocative moral ambiguity - and more often than not, it succeeds. In that fashion, it's reminiscent of Dennis Hopper's stark crime melodrama ``Colors,'' which combined urban hyper-reality with a savvy portrayal of cops just working their beats.

Moreover, the cast's excellence just begins with Chiklis - all involved bring their distinctive, original characters to vivid life, so that even when the storytelling threatens to go over the top, we're still engaged out of curiosity as to how the characters will react. Grainy, hand-held camera work lends the series a further urgency and sense of excitement.

Some may find ``The Shield'' too explicit for their tastes, but the truth is probably that most other cop shows are too tame.

THE SHIELD - Three stars

What: Second-season premiere of the gritty cop series starring Emmy winner Michael Chiklis.

Where: FX.

When: 10 tonight.

In a nutshell: Rough, compelling and pretty smart in a graphic sort of way.