Genre Conventions Undermine `Stranger'

XX 1/2 "A Stranger Among Us," with Melanie Griffith, Eric Thal, John Pankow, Tracy Pollan, Lee Richardson, Mia Sara, Jamey Sheridan. Directed by Sidney Lumet, from a script by Robert J. Avrech. Alderwood, Aurora Village, Crossroads, Everett Mall, Kirkland Parkplace, Renton Village, Uptown. "PG-13" - Parental guidance advised, due to language, violence. --------------------------------------------------------------- Although it's enjoyable as a bittersweet, fish-out-of-water love story, Sidney Lumet's "A Stranger Among Us" is less effective when it transforms itself into an exotic whodunit.

Set in New York's Hassidic community, where a young man has disappeared along with $720,000 in diamonds, Robert J. Avrech's original screenplay focuses on an aggressive female police detective who is ordered to give up her gun-happy tactics and go undercover.

Disguised as an orthodox Jewish worker, she falls in love with a young rabbi (Eric Thal) who is engaged to a woman he's never met. She also befriends his sister (Mia Sara) and their apparent father (Lee Richardson), while her hospitalized partner (Jamey Sheridan) and anti-Semitic assistant (John Pankow) try to convince her that they're more her style.

Melanie Griffith, who is making more movies these days than Cher or Meryl Streep, plays this Dirty Harriette in the same breezily superior fashion she brought to the role of a Nancy Drew-like spy in Nazi Germany in "Shining Through."

She's so much smarter than her new Hassidic friends that she immediately spies the missing man's corpse tucked away in a blood-stained ceiling. A veteran of the streets, she's so cynical about human behavior that she can announce to a concentration-camp survivor that "inside every honest man is a thief waiting to get out." Although she claims to be a spectacularly happy independent woman, she appears to spend much of her off-duty time alone, watching Astaire-and-Rogers videotapes in her underwear.

What's missing in her life is the sense of community she recognizes in the way these people live, work and worship. Especially after a frustrating visit with her macho father and a few run-ins with other cops, she learns to value her new friendships and wonders if she could fit into this world. Unfortunately, as soon as Avrech starts to raise these questions seriously, the movie returns to the thoroughly routine matter of flushing out the thief and killer.

Like David Mamet's "Homicide" and Lumet's own recent police drama, "Q and A," the movie works best when it's investigating a specific urban subculture. It misses when it returns to genre conventions. Best known as the co-writer of Brian De Palma's "Body Double" (the 1984 vehicle that made a star of Griffith), Avrech had an orthodox upbringing in Brooklyn, and his script is fleshed out with details about Hassidic traditions that carry the weight of authenticity.

Griffith is affectingly vulnerable in the central role, even if her performance seems lightweight for a cop who's been criticized as a vigilante. Even better is Eric Thal, who was originally cast in a smaller part but was eventually elevated to Griffith's co-star. He more than justifies Lumet's confidence in him.