The shadowy "Chinatown" evoked by Robert Towne in his famous movie of the same title lingers as the best single metaphor in recent filmmaking. In the book "The Craft of the Screenwriter," Towne recalled how the idea was suggested by a conversation with a former Los Angeles vice cop. "Down there," Towne's informant recalled, "you don't know who's a crook and who isn't a crook. You don't know who you're helping and who you're hurting."

Towne used this terra incognita to suggest the way good intentions are repeatedly undermined by ignorance and misconception. In that respect, it's a locale that haunts all of us.

"Chan Is Missing," opening today at the Dupont Circle, hints at intimate acquaintance with an authentic Chinatown. It's a shoestring feature (the official budget was about $20,000) that was well received at a "New Directors" festival in New York last year and recently received a special award from the Los Angeles Film Critics.

The film was shot predominantly in San Francisco's Chinatown by Wayne Wang, a 34-year-old naturalized American who was born and raised in Hong Kong and immigrated to the Bay Area. There he pursued a career in local TV documentary production before attempting this feature breakthrough, subsidized with grants from the American Film Institute and the National Endowment for the Arts.

At the outset you sit up and take notice, because it would be interesting and satisfying to see "Chan Is Missing" fulfill its promise and emerge as a fresh sort of ethnic entertainment--the first sociologically probing and revealing mystery-melodrama made from inside a Chinese-American urban culture. Regrettably, Wang isn't nearly as conscientious or resourceful as he needs to be in order to capitalize on that initially promising element of authenticity.

"Chan Is Missing" proves to be a better pretext for a movie than a finished film. The smart title, a jaunty opening (a cab radio emits the delightful sound of "Rock Around the Clock" as sung by a Cantonese group) and the intriguing premise sustain perhaps a reel's worth of genuine, unflagging, unpatronizing interest. When it becomes tiresomely apparent that Wang can't get the exposition out of low gear, the movie grinds to a standstill.

The original mystery element, indicated in the title itself, is brushed off as a matter of trifling consequence, probably because Wang and his cowriters couldn't really invent a sustained narrative. Even more damaging, the sociological revelations and insights about the inner workings of Chinatown, which are supposed to transcend the original mystery, turn out to be disappointing, trite, superficial and inconclusive.

The title refers to a Taiwanese middleman who has vanished with $4,000 belonging to the principal characters--a patient middle-aged cabbie named Jo (Wood Moy) and his sarcastic young nephew Steve (Marc Hayashi), who had pooled their savings in order to secure a hack of their own. The efforts of these likable amateur sleuths--an amusing, self-aware variation on the format of the Charlie Chan stories--to locate their missing business agent is meant to uncover a wealth of inside information and dramatization about the social patterns, contradictions and conflicts that exist within the Chinese-American community.

Wang suggests that we'll learn something about the way things really work, who the power brokers are and how they operate, as a result of tagging along with Jo and Steve. In particular, he hints at an emerging power struggle between groups loyal to the old Taiwanese business elite and rivals attracted by fresh money and prospects from Communist China.

The fleeting, tentative impressions actually made by the movie are bound to invite a letdown after such a novel come-on. Wang appears to be something of a tease on the documentary side--he may know far less about the way things work than he dares admit. Since it's obvious that he also lacks the pictorial or writing skill to compensate for the once-over-lightly social insights, there's really nothing left to fall back on except Being Tolerant of a groping new talent. In this case, the audience is obliged to tolerate an abundance of patchy, inert 16mm footage on top of the exaggerated, unfulfilled expectations.

Rave snippets like "A Matchless Delight," abstracted from The New York Times review, may also help to set up the viewer for a fall. If you approach "Chan" with very modest expectations, the possibilities in the material may seem interesting enough to offset some of the ultimate shortcomings, but it's unrealistic to anticipate a higher order of esthetic stimulation. At best, you feel that Wang introduces a few things that ought to be developed more astutely, especially a young performer as keen as Marc Hayashi, whose work does suggest fresh, funny ethnic angles. His Steve is a streetwise Chinese-American kid whose sense of humor has been heavily influenced by Richard Pryor.

It might have been hilarious if the Eddie Murphy character in "48 Hrs." had run into Hayashi's character, since both owe so much inspiration to the same source. Seeing Chinatown haze out in grainy, raggedy, black-and-white images also persuades one that it's a setting that really cries out for the flamboyant, nocturnal color stylization used in "48 Hrs." The unhappy irony of "Chan Is Missing" is that it misses the opportunity to evoke either a mysterious or an authentic Chinatown.