Forty feet above an awestruck crowd of 300, a nude, hairless man and woman hang from industrial-strength cables affixed to the underside of the First St. Bridge in Downtown L.A. It's about 9 p.m. Intense red lights bathe the duo in the color of blood. Harsh, scraping, industrial music -- augmented by police helicopters overhead and locomotives groaning towards a nearby train station ­- shrieks from a set of speakers. The man and the woman are several feet apart, each hanging head down from their own ropes. Their hands reach towards each other, straining to touch. The effort is futile and pathetic. Their bodies then stiffen into the first of many bizarre poses.

So begins a 60-minute Kafka-cum-Butoh dance performance spectacle from the internationally renowned duo known as Osseus Labyrint. OL is Hannah Sim, 37, and Mark Steger, 38. They have performed their insect-inspired dances of death and rebirth in a number of exotic locales worldwide: a mental asylum in Czechoslovakia; an ancient barn in Austria; and a Turkish bathhouse in Hungary. Tonight, however, they're on home turf. Well, sort of. Though the bald-headed pair is based in L.A., this is their first time hanging from a bridge. There's no net below to catch them if they fall, only the concrete bank of the L.A. River.

About half of the act takes place in mid-air. Sim and Steger twist about into such insane, altered states that they lose all identity or sex, save for Sim's bare figlet or Steger's flapping manhood. They look like refugees from Roswell or the subjects of some WWII Nazi experiment. Eventually, they lower themselves to the ground, where the remainder of the performance takes place. They crawl after the manner of caterpillars and walk about on all fours like spastic dogs. Perhaps they've hopped out of some film by David Lynch or Eadweard Muybridge. For the audience, drawn to this underground event by word of mouth, Osseus Labyrint have eclipsed their own humanity, mutating into otherworldly creatures, both fascinating and horrific.

"Osseus Labyrint is the bone in your skull that regulates balance, your inner ear," Sim explains several days after the performance, perched on the couch of the walk-up apartment she shares with Steger in central L.A. "Back when we were beginning 10 years ago, we made this huge list of words that meant something to us. After looking at it, we realized there were a couple of themes: one of them was structures or bones; the other was chaos, entropy, labyrinth. So we tried to find a phrase that meant both things. Finally, we got Osseus Labyrint."

"For the first year or two, we would just go to a park and start throwing each other around," she says, pausing from time to time to stretch her long, thin legs. "They were jam sessions, basically."

Sim, an enchanting, pale creature, says they eventually invited in others to help create soundscapes and sets. One day, they wondered what it would be like to hang upside down, and so began their signature gravity-defying stunts.

"We feel like we can inhabit any environment if we have to," she laughs. "We'd like to be the first artists in space."

Steger, the quieter of the two, is busy packing their bags. In an hour, they have to be at the Coachella outdoor music festival to perform with Tool. He stops from time to time, to comment. He says their shaven heads were an attempt to strip away all defining characteristics.

"We'll even watch a videotape sometimes of our performance, and there'll be moments where we're not sure who's who," says Steger.

Nudity was another way of removing everything extraneous.

"Part of what we do is about the history of the body," says Steger. "It makes sense to show it."

"Animals aren't embarrassed to be naked," says Sim. "I don't even think about being naked unless I'm cold."

That evening under the First St. Bridge was chilly. Most of the audience members were wearing jackets. Seated on a steep incline that formed part of the bridge, some took swigs from whisky flasks. There was also the smell of the L.A. River, a garbage-strewn stream of street runoff and treated sewage. On its sides, there are the encampments of homeless who use the slime-filled waterway as a toilet.

All of this made OL's next move a stunning coup d'état, one that left everyone gasping. After wiggling here and there spasmodically on the ground for some time, they froze, as if in suspended animation. Two production assistants emerged from the darkness, lifted Sim and Steger one-by-one, and tossed them into the river. They swam off out of sight, along with the current.

Afterwards friends asked if they had gotten tetanus shots. They say they hadn't, and apparently they haven't caught anything horrendous. For Sim and Steger, it was just one in a long line of risks they continue to take with their performances.

"Life can't always be safe," says Sim of the experience. "Danger is part of living, too."

Stephen Lemons is a full-time writer and sex-fiend who contributes frequently to New Times L.A., the Los Angeles Times, Art Connoisseur, and SOMA magazine.