In “Narc,” Ray Liotta is one scary proposition. As Lt. Henry Oak, a Detroit cop who’s bent on avenging the death of a partner, he’s lit up with anger. Those eyes burn like a husky’s. A crazy husky. But what makes Henry truly creepy is his ability to keep his nuclear fury under wraps.

The story’s actually about Nick Tellis (Jason Patric), an undercover narcotics cop who has gone too far. When a suspect he’s chasing runs into a playground, Nick fires anyway.

A pregnant woman is wounded and, ultimately, loses the baby. Nick, who has a wife (Krista Bridges) and child, is facing continued suspension or worse. That is, until the police board offers him an alternative: to solve the murder of another narc, brutally killed. The dead man was Henry Oak’s partner, and Henry isn’t looking to bring the perpetrator to legal justice. He wants revenge. And Nick has to work with him.

It’s the beginning of a nasty assault on every bum, hooker and addict they can find and beat up. Judging by Henry’s bloody agenda, you can smell something horrible in the offing. And when the partners close in on their quarry, you brace yourself for a grim showdown — worse than anything you’ve already seen.

Writer-director Joe Carnahan, who made the indie “Blood Guts Bullets & Octane,” has a video-store clerk’s appreciation of cop and crime cliches. And he sows a well-sustained allegory-cum-cop drama. But there isn’t a stylistic, thematic or story detail that hasn’t been drummed and redrummed into our moviegoing and televiewing subconsciousness.

What “Narc” does is put it all together in a well-stuffed body bag of intensity. This is a stirring movie, if relentless intensity, handheld camera work, cover-your-eyes violence and ear-splitting yelling matches are what you’re craving. If violence and intensity could be rated on a scale of one to 10, this movie — like the misguided guitarist in “This is Spinal Tap” — aims for 11.

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Liotta’s performance is powerful indeed. It pushes the envelope in the kind of role that already demands you push the envelope. But “Narc” also aims to turn Henry Oak into an almost Shakespearean character, who deserves more than superficial moral scrutiny. Naaa. He’s just an unhinged guy with a violence problem. And he doesn’t deserve dramaturgical appreciation so much as time served.