Some new shows come and go without notice. That won’t happen with “The Shield” (9 p.m., FX). This excellent, gritty, challenging, compelling and consistently surprising cop drama explodes on the screen and jumps into the ranks of one of television’s best dramas.

Michael Chiklis ( “The Commish”) stars as Detective Vic Mackey, the head of an elite strike force assigned to clean up one of Los Angeles’ most gang-ridden neighborhoods. Mackey and his team succeed all too well by bending the law until it is barely recognizable. Mackey beats up perpetrators, pits drug dealers against each other and seems to have a cozy relationship with streetwalkers. To his supporters, he’s brutal but effective. To his enemies, including Capt. David Aceveda (Benito Martinez), he’s “Al Capone with a badge.”

Chiklis has carved out a role of lifetime here. With his icy blue eyes and nervous, gum-chewing demeanor, Mackey is a tightly wound cobra. No character this side of “The Sopranos” does as good a job conveying an ever-present potential for violence.

Outside of his task force, Mackey’s colleagues treat him with a combination of awe, resignation and active contempt. In tonight’s episode, Aceveda organizes a sting to bring Mackey down. Only it’s not clear if he’s out for justice or merely to advance his own career. Detective Claudette Wyms (CCH Pounder) takes a more philosophical approach. If one rogue cop can make the streets safe, let him loose.

Wyms and Detective “Dutch” Wagenbach (played with marvelous restraint by Jay Karnes) provide “The Shield’s” calm dramatic center. They spend most of tonight’s episode interrogating dreadful child-molesting suspects, employing “good-cop bad-cop” head games. But when one creep fails to crack, Mackey calmly arrives as “a different kind of cop.”

Not for the squeamish, “The Shield” is awash with enough violence, profanity, perversion and sexual situations to make “NYPD Blue” and “Philly” seem tame. But unlike too many episodes of those Steven Bochco dramas, the adult subject matter on “The Shield” always seems genuine and never forced or gratuitously cute. “The Shield” deserves to be compared with the best cable dramas. So far, it falls short of “The Sopranos”‘ depth of character development. We see Mackey has a wife and children, but we have no clue as to their relationship. But it’s a sign of a good show and effective writing that you want to know more about such strong characters.

Tonight’s other highlights

On back-to-back episodes of “Frasier” (NBC), Frasier gets a younger agent (Kristin Chenoweth) (7 p.m.), Frederick enters a spelling bee (8 p.m.). The first episode is a repeat.

Ben Stiller guest stars on the season finale of “Undeclared” (7:30 p.m., Fox)

A boy seeks to stop an adoption that would separate him from his brother on “The Guardian” (8 p.m., CBS).

Palmer and Jack meet for the first time on “24” (8 p.m., Fox).