Blake Edwards has long been one of our most successful directors, though not one of our best. In movies like "10" and "S.O.B.," he became a sort of parody of an auteur -- he didn't make personal films, but self-serving ones.

But in "Micki and Maude," working for once with someone else's script, Edwards finds new life. Billed as a romantic comedy, the movie is certainly funny, but it's also as darkly disturbing as any this year.

Rob Salinger (Dudley Moore) toils as a correspondent for a happy-talk local TV show called "America Hey!"; his wife, Micki (Ann Reinking), is a workaholic lawyer who has to make appointments to see him. When Micki typically cancels their dinner date, Rob accepts the invitation of a cellist, Maude (Amy Irving), to hear her play with a string quartet. Drunk, enchanted, and frustrated with his marriage, Rob shares her bed.

Rob feels guilty about what he's done -- he's a family man, in fact too much of one. When Maude gets pregnant, he decides to marry her; at which point Micki announces her own pregnancy, having decided that raising a family was more important than her career. For a man obsessed with having a child, what could be better than having two? So Rob undertakes a double life as the bigamist husband of both women. "If I don't get bedsores and the San Diego Freeway doesn't collapse," he says, "I'll be okay."

The story is simple, and Edwards and first-time screenwriter Jonathan Reynolds hew to it, mining its considerable comic potential. Rob and his best man, Leo (Richard Mulligan), drive over to Rob's second wedding; naturally, they run into Micki's parents, out for a stroll. The morning-suited duo fumble for an explanation, spinning out a tale of a "gangster wedding" that becomes increasingly bizarre, while discovery waits just inside the church door. Edwards shoots the scene in an excruciatingly long take -- Rob's edgy discomfort comes straight across the screen, undiluted by fancy editing or camera work. By just letting his camera sit still, Edwards evokes the claustrophobia of the boxes-within-boxes of deception.

Edwards can be crude in his use of visual gags, and Moore the most obvious of physical comedians (his recent movies are just setups for watching him fall down). But here the slapstick grows out of the situation, rather than being tacked onto it. The two women use gynecologists who share offices -- of course, their appointments coincide, giving rise to an expertly choreographed entrance-and-exit shtick out of the Marx Brothers. Flitting from woman to woman as they float gingerly with their newly inflated bodies, Moore looks like a space probe journeying between twin planets.

More important, the slapstick is underplayed, accorded its proper place far from the center of the movie. Slapstick is the comedy of the victim -- at the first sign of trouble, the nerves disintegrate, the limbs go on the fritz. But in "Micki and Maude," the comedy stems from the relief you feel when you watch someone skirt disaster, then triumph over it. Constantly confronted by his wives with the inevitable inconsistencies in his behavior, Rob has to come up with new stories to explain them away. When Micki, for example, discovers the "I Love You" that Maude had penned on the label of a sweater she gave him, Rob tells her that he wrote it himself -- he's insecure, and needs to know that at least he loves himself.

Rob's elaborate ruse calls on creative resources he never thought he had, in the same way that this role calls on things inside Moore that he hasn't shown before. Who expected Dudley Moore to be a cerebral actor? In "Micki and Maude," Moore gives a performance in which you can see his wheels spinning, in which the style comes not from pratfalls but from language. He projects such quiet charm that you can hardly believe it's the same guy. And this usually stagy showoff demonstrates genuine spontaneity here, in a brief shot toward the beginning when he laughs at himself, or in the delightful, improvisatory feeling he generates with Mulligan (who also gives one of his best, most relaxed performances).

With her knowing eyes and exotic beauty, Irving generates more heat on the screen than almost any actress around -- her face spreads out like a bird in flight. In "Micki and Maude," she continues to reveal the flair for comedy she showed in "Yentl," particularly when she mimics Godzilla as she and Moore watch a late-night horror movie. The biggest flaw in the movie is Reinking. As a high-powered lawyer, she's not believable for a second; worse, her twitching, actressy style can't compete with Irving's innate sexiness. In a contest between the two, anyone would opt for divorce.

Reinking's not the only glitch. Edwards' tired signature pokes through here and there (Moore kicks over a fire extinguisher and, ho ho, look at the suds!). Reynolds' one-liners can be lame ("Does a sonogram hurt?" "Only if it's a singing sonogram"). And Moore can be cloying when he lapses into his Cuddly Dudley riff, talking in a kiddy voice or sharing an egg roll with a cat. What saves him is the context of bigamy, in which the cuddliness seems perverse -- who does he think he's kidding? Edwards shoots these scenes with more long takes that make the cutesiness seem flat and studied; what's left is the dregs of cynicism.

In Reynolds' script, Edwards has found a home for his themes that elevates them far above any stories he's concocted himself. Edwards is obsessed with marital infidelity, but his movies miniaturize it -- in "10," Bo Derek is an adolescent fantasy, not a mature one. In "Micki and Maude," by contrast, the urge to cheat is wrapped up with the urge to procreate, something no one could call negligible. Rob claims to love these women, but what he really wants is to replicate himself -- he's stuck inside his own head, so the "I Love You" on his sweater label has an ironic, revealing spin. As the two women come to join Rob in his deception, "Micki and Maude" creates a world of egomaniacs who can relate to each other only through duplicity. Its final image of Moore dandling his children has an eerie, unsettling aura. See how they grow up. "Micki and Maude," opening today at area theaters, is rated PG-13 for occasional profanity and sexual themes.