IT'S NO MYSTERY WHY 'PRIME SUSPECT' IS SO WATCHABLE.

Byline: Frederic M. Briddle Boston Globe

The latest exhibit in TV's top crime drama, "Prime Suspect: Inner Circles" (Sunday, PBS), is gripping, provocative and most of the other four-star descriptives a critic might hack into a review. That said, it's time for Inspector Jane Tennison to pour her favored whiskey and soda, sit back and consider turning in her badge.

Certainly, the "Prime Suspect" way with crimes and characters - which are so seamy they're cross-stitched - is undiminished. So is Helen Mirren's pressure-cooker acting, which lures us under the lid she barely keeps on Tennison's roiling, contradictory emotions: tenderness, vulnerability, damnable stoicism.

But until now, these sustained a unique study of a woman's professional rise in a world of brutal power relationships. Tennison transcended sexism while solving the murders of black women in "Prime Suspect II" and boy prostitutes in "III" - victims even more despised by British society than she was within her London precinct.

Oh, how Jane felt their pain. And along the way, she forfeited her identity for the sake of career. In last October's "Prime Suspect: The Lost Child," the dynamic had reached its limit: A pedophile proved a red herring for the real child killer, the mother. We shivered with irony, and so did Jane, who, after all, had agonized over an abortion in the previous installment of the series.

This time, irony is beside the point. Instead of the gutter, the principal scene of the crime is that upper-class haunt, a suburban country club. When the manager is found dead, pants pulled down and gruesomely bug-eyed after the killer's lame attempt to disguise murder as autoerotic strangulation, our crime lover's taste buds water. But spelunking for a killer in the land of high tea and crumpets smacks of Miss Marple - and that's precisely the mold "Prime Suspect" broke to become great.

Writer Eric Deacon quickly wheels "Inner Circles" back to the wrong side of the tracks, as the victim is revealed to have been murdered over a fraudulent scheme to make abandoned luxury condos out of a public housing project. But unraveling the complex fraud, and a second murder that indirectly results, taxes Tennison's intellect - and the viewer's - to distraction. The plot works out, but the energy required leaves scant room for writer or viewer to consider its significance to Tennison.

Having been promoted again, she's solving a crime outside her old jurisdiction, and thus must overstep the local precinct inspector, a man. The clubby preserve of the Huntington equally resents her presence. Yet this class conflict is not only simplistic but unconvincing, given that Jane herself is a power to be reckoned with at this point, and no slouch (even if she looks like one). Although the projects are the setting for the second murder, every suspect is upper-class, or the scion of such. This doesn't resonate, because unlike in the last "Prime Suspect," Tennison is never in doubt about the perpetrator, nor is the viewer.

Meanwhile, Jane's ever-dimming personal life, once a crucial "Prime Suspect" subplot, has been reduced to a punch line. Instead, the secondary focus is on Detective Sgt. Chris Cromwell (Sophie Stanton), one of the suburban detectives Tennison deploys. Of course, she turns out to be a young Tennison, yet catches hell under her temporary boss, who's determined not to be perceived as a reverse chauvinist.

These and several other plot developments are flawlessly played ... cliches. Didn't we just see Detective Pembleton grapple with jurisdictional boundaries on Wednesday's "Law & Order"? Isn't the one about the cop who's married to her job as old as "Cagney & Lacey"? And as for introducing a chip off the old block (as fine a chip as Stanton is) - well, isn't that too cute?

Not even these lapses make "Prime Suspect: Inner Circles" less than compulsively watchable. The producers haven't hired Joe Pesci for comic relief yet, as did "Lethal Weapon." Nor have they negotiated a crossover effort with "Homicide" or "NYPD Blue." But I can almost see that coming.

Having made all of its points brilliantly, "Prime Suspect" may have nothing new to offer but gimmickry. Still, I'd do time before I missed the next installment, "The Scent of Darkness," due this spring.

Meanwhile, Helen Mirren, one hopes, will take a cue from other actresses who exited the projects they'll always be remembered for - Lucy, Mary, even the geniuses of "Absolutely Fabulous," from Mirren's own Britain. Knowing when to quit is sometimes the greatest mystery of all.

THE FACTS

The miniseries: "Prime Suspect: Inner Circles"

When: 9 p.m. Sunday.

Channel: KCET (Channel 28).

Starring: Helen Mirren.