A rogue-cop drama with such robust performances and realistic grit that its flirtation with clichés hardly matters, "Narc" strives to bring back the tough authenticity of 1970s police flicks like "Serpico" and "The French Connection."

Jason Patric ("Sleepers") stars as a defiant undercover narcotics badge, struggling his way back into the good graces of the department after being suspended for a shooting, the guilt of which haunts him every day.

The film opens with an over-the-shoulder point-of-view foot chase -- an adrenaline-pumped scramble over fences and through the projects -- that ends with a pregnant bystander losing her baby. It's the incident that landed Patric on paid leave and in a detox program while his own pregnant wife stood by him.

Pushed back into Detroit's drug underworld by a department that needs his still intact cover to investigate the killing of another undercover cop, Patric is paired with Ray Liotta, playing the slain man's vengeful partner, who has no qualms about stomping on the rule book when it serves his own perception of the Greater Good.

As written and directed by Joe Carnahan (whose $7,000 feature "Blood, Guts, Bullets and Octane" made a small splash in 1998), these two detectives are uncommonly unaffected, not just as ardent, hardboiled cops, but as husbands and human beings with their own separate codes of ethics. And as played by the dedicated Patric and Liotta, they leap off the screen with depth and dimension.

"I tell you this," says anguished, widowed Liotta in the kind of guard-dropping heart-to-heart that can arise between tough cops only a during long stakeout, "I became a much better cop the day she died. Any hesitation I had was gone. I'd see a deadbolt door, I'd kick it down -- the first in the room."

This is strong stuff, and both story and characters turn even more engrossing when Patric's investigation comes up against barriers and inconsistencies in the accounts of Liotta's partner's death. Why is access to the files on the dead cop's wife restricted? Was he crooked? Had be become an addict? Why does Liotta blow his top when Patric questions the widow? Is he instigating a cover-up to save the man's reputation and survivor's benefits? Or is he perhaps trying to hide his own duplicity? The guy is shady and wrathful, after all, and willing to beat and threaten suspects in his own manner of justice even though he's already been threatened with indictments for misconduct.

"I'm gonna bag the montherf***ers that killed Mike, and if that means breaking every procedure, they're broke," the graying, vein-popping, life-long cop rages. "His life was worth more than a wreath and a rifle salute."

As conflict between the two cops increases, Carnahan carves new creativity into a familiar genre that's rife with pitfalls, platitudes, shootouts and chases. The story doesn't contain many surprises, but neither is it predictable. It's tense, vividly character driven and not dependent on stock cop character traits. It's refreshing to see a sober movie cop like the one Patric plays, who puts as much effort into being a good father and husband as he does into being a good detective embroiled in his street-scum cover, even as he's troubled on both fronts.

The film is also vividly photographed and edited (a creative, four-quadrant montage shows Patric and Liotta rousting riff-raff for information), giving the film a fresh aesthetic edge.

Ultimately, "Narc" still treads on well-worn ground. But it's such a deeply felt effort with such dedicated performances that it rises above any potential triviality on the strength of Carnahan's stalwart determination to be true to his multifaceted characters and their anything-but-black-and-white world of sullied ethics and malicious street justice.