"Chan Is Missing" is something of a Chinese-American puzzle. It's a unique mystery featuring the most endearing sleuth since Miss Marple. There are plenty of clues to ponder, but they're inscrutable. It's a neo- neo-realistic "Rashomon," a film without an ending. It just stops dead.

Though disappointing, "Chan" is a showcase for director Wayne Wang's virtuosity. The film is grainy, gutsy art, all black-and- white, low-budget ($20,000) brilliance. Wang's revelation is close-up: He shows us the pores of Chinese America, a place so alien that black and white Americans haven't even managed to work up a ghetto stereotype.

The actors, as naive as though Grandma Moses had painted them, are all Asian Americans and they perform in the streets, offices and kitchens of San Francisco's Chinatown. There's a cook in a Samurai Night Fever T-shirt who makes five orders of sweet-and-sour pork. There's a final montage of faces and storefronts where a Buddha sits centered in Christmas tinsel -- all to the tune of "Grant Avenue, San Francisco. . . U.S.A."

The film's protagonist, a cabbie called Jo, is played by Wood Moy, whose benign, crumpled face is as round as the rim of a teacup. He and his nephew Steve (Marc Hayashi), a modern wiseacre with a mouth full of Richard Pryor jokes, entrust their savings to a hustler named Chan Hung, who offers to get them into the taxi business. When Chan disappears a few days later, it seems he's absconded with the loot. And we're on a bus tour as the amiable pair search Chinatown for clues, dispensing none-too-subtle dollops of cultural awareness along the way.

Says Jo, "If this were a TV mystery, an important clue would pop up now and clarify everything." But it doesn't, and as Mr. Fong tells Jo, and us, "You have to think Chinese to solve the mystery." That means, use the negative to get to the positive. As Jo himself says, "I guess I'm not Chinese enough to accept a mystery without a solution." CHAN IS MISSING -- Dupont Circle.