Sex is gross. Maybe it's visually gross, anyway, clumsy and unaesthetic to the ones who are not involved. No wonder filmmakers have been using either dance or exercise as metaphors for sex, in ways as different as Astaire and Rogers are from Flashdance. The actual getting-down, the selfish, sweaty, repetitive craziness, is on some level visually offensive to the non-turned on. Or at least those who pretend not to be.

People who chuckled at the dirtiness of the "A to M" jokes in Clerks II will choke on Shortbus, where it actually happens. If they snickered over Brokeback Mountain, they'll walk out by the titles. Shortbus features explicit sex: recreational, polymorphous, homo and hetero. What can we do but concede? Sure, it's gross. Maybe it opposes other methods of grossness: gross consumption, gross horror. At least, it's pleasantly gross.

John Cameron Mitchell of Hedwig and the Angry Inch assembled an improvisatory cast and then worked with them to see how far they could go. Consciously or unconciously, Mitchell combined the plot of two porn movies, Behind the Green Door and Deep Throat.

A sex counselor named Sofia (Sook-Yin Lee) has been faking satisfaction ever since she was married. Still, she pursues a ridiculously athletic sex life; at one point, she's taken, braced on the keyboard of a piano. "I feel sorry for people who can't have what we have," she says, lying to her husband with a wide, almost scary smile. If you wanted someone to defuse a frightening subject like sex, Lee is the perfect actress—small, herbivorous-looking, embodying a Canadian gentleness (she's a TV personality up there).

Sofia tearfully blurts out the truth to two of her patients, a pair of unhappy gay clones called James and Jamie (Paul Dawson II and Paul DeBoy). They urge her to attend an illegal salon called Shortbus in a forbidden part of town. There she meets someone to whom we have already been introduced: an ornery dominatrix/artist named Severin (Lindsay Beamish) who has a high-rise office overlooking the bloody stump of the WTC. Severin tries to therapize the therapist. Unfortunately, Sofia is just as liable as to fall victim to a false epiphany as any of her clients.

James and Jamie try to spice up their love life with a third partner, but the new man finds interest in the two of them only as a set—they seem like such a perfect couple. And Jamie is aching to set out on his own, one way or another. (The two had been previously known as "James and James"—changing his name was Jamie's first step on the road out.)

The visitors at Shortbus, a sex cabaret with an orgy room, help provide support for these crises. Justin Bond, a well-known cabaret figure, has the role of "Brothel Madame." Our cinema is loaded with witty gay male quippers, but Bond is the only genuinely funny one I've seen in a long time. Someone likens the club to Gertrude Stein's lair, and Bond replies, "That sounds like a real weenie-shrinker." When we see into the orgy room, sitting in the roiling flesh is someone taking notes: no doubt hard at work philosophizing how it feels to witness an orgy. "Voyeurism is participating," Bond says, opposing the motto of Burning Man.

Actually, Shortbus is a lovable film for neither overintellectualizing or overdramatizing the plights of its characters—movies with sex are traditionally held together with drama instead of comedy. We see a plaque reading "New York Sensory Deprivation Center—Fourth Floor;" one unfortunate comes to after an overdose in "Our Lady of Adequate Mercy Hospital."

Still, Shortbus has a center. In the numbness of two characters who are calloused by sex work, Mitchell reflects the cruel, conformist and deadening world of mainstream porn. Maybe better than anything in Angels in America is a scene of a former mayor of New York prowling the club Shortbus' corridors. He is a tortoisey old man looking for forgiveness for what he failed to accomplish during the AIDS crisis.

Mitchell holds the film together with shots of a cardboard and tempera city, over which a camera gyres and gimbals. Compare the unthreatening kid stuff of Michel Gondry's sets in The Science of Sleep to Mitchell's cardboard Manhattan, a maze of buildings around the thick and dangerous forest of Central Park. This city comes alive with sexual energy, but it is plagued by brown-outs—misunderstandings causing a disturbance in the sexual force.

The wall between porn and nonporn will come down. Filmmakers as different as Lars von Trier, Wayne Wang and Catherine Breillat have made holes in it already. Mitchell's tart, sweet but never sloppy film puts it ahead of the pack. Shortbus is not the work of a fraud, a pornographer pretending to be an artist. Sometimes the actors fail, some situations aren't as compelling as others and Mitchell has trouble wrapping his film up. Still, Shortbus is everything an underground movie ought to be: a joy, a threat to the established order and a celebration of messy urban life and what Mitchell describes as "permeability"—the ability to let ideas and other people through the armor.

Shortbus (Unrated, 102 min.), directed and written by John Cameron Mitchell, photographed by Frank G. DeMarco, opens Oct. 13.

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