One way of exploring how close two people can be while still remaining separate is to do what identical twins Michael and Mark Polish did for their film "Twin Falls Idaho." They strapped themselves into a body harness to portray brothers connected from the shoulder down to a shared middle leg.

Playing conjoined twins was excruciating physically, they confess, standing up at a Hollywood restaurant to demonstrate. Michael folded his leg behind him to play Francis, the weaker of the two conjoined brothers, and each of them had to strap one arm behind the other to give the illusion of a single organism, all under a latex harness that was covered with flesh-colored fabric.

On top of that, they wore a specially tailored brown wool suit. Underneath, they each sweated off about one pound a day. At the end of each shoot, they would collapse, exhausted. Still, Michael says, "I didn't mind it that much--well, your ribs would hurt."

Their portrayals of Francis and Blake Falls and their relationship with a lonely prostitute, Penny, allowed the 28-year-old filmmakers to investigate their own bond as identical twins. The brothers are so close that they finish each other's sentences. Spookier still, they often allow one to speak for the pair, and yet the listener knows somehow that the second twin is in agreement. But they insist that the conjoined siblings in their film are also meant as a metaphor for any longtime couple about whom one might ask: Where does one person end and the other begin?

The movie "is about how loneliness can be with people who are very close," says Michael, barely audible in a garish diner at the Best Western in Hollywood, a down-market locus of hipster L.A. He continues, "About how loneliness is not just about not being with someone. It has a lot to do with the brain. It's not physical."

(Mark is wearing a smooth black cap; Michael's light brown hair is longish and frames his angular, unshaven face. An interviewer is grateful for these distinguishing clues.)

Francis and Blake, Michael goes on, are "completely close. But they can have different personalities. Different relationships with people. And ultimately, cooperation."

When Mark finally joins the conversation, it's to echo his twin: "It's exploring the relationship between twins. Or siblings. Or a married couple of 50 years. It's an exploration of a relationship that is a strong, unique bond. Ultimately the bond of flesh is a metaphor for love."

Binary Stars

It is nearly impossible to tell the Polish brothers apart; they are both long-limbed, painfully thin, hawk-nosed and pale, like figures from a Modigliani painting. As with many identical twins, they seem almost metaphysically connected, speaking with the same intonation, the same gestures, the same instincts. As small children, their mother sent them to a speech therapist so they would learn to talk in full sentences instead of the half-phrases they exchanged with one another.

Even asking them now how they differ, the brothers respond with a thoughtful stare instead of a ready list of disparities.

"Mike's calmer," says Mark. "I philosophize stuff more."

Long, long pause. Finally Michael volunteers: "We don't have any huge competitiveness . . . "

" . . . Or separation anxiety," Mark finishes the thought.

Still, before deciding to create "Twin Falls Idaho," the filmmakers were mainly looking for a subject they could make cheaply. A bigger-budget film they had written hadn't sold, and they wanted one they could write, direct and star in themselves. Mark and Michael had long been fascinated with Chang and Eng Bunker, famous 19th-century conjoined twins who were a successful sideshow act, each of whom married and had children. The more the Polish twins thought about it, the more it seemed like the germ of an idea.

"I think a lot of people are fascinated by Siamese twins," says Michael. "What gave us the insight was that we could play it. The image inspired us."

Their poetic, moody film about Francis and Blake is notable not only for its treatment of an unusual subject, but also for its treatment of the subject with empathy and sensitivity. The brothers, as portrayed in the film, are neither freaks nor weirdos; they are merely creatures who inhabit their own particular world. They speak in a private, whispered shorthand and inhabit a seedy motel on Idaho Street where they befriend a prostitute named Penny, played by newcomer Michele Hicks. They try (and fail) to engage her services, but a relationship develops between Blake and Penny as the film deftly touches on mysterious issues of individuality, identity and human interdependence.

A first effort with a tiny half-million-dollar budget, the film has nonetheless received more than its share of attention, winning early praise from New York Times critic Janet Maslin after the Museum of Modern Art in New York held a screening, and sparking a buzz at this year's Sundance Film Festival, where it was bought by Sony Pictures Classics. One glowing review in the Boston Globe called the film "shadowy, enticingly eerie and . . . tantalizingly original," while the Los Angeles Times praised it as "infinitely moving."

Bodies and Soul

The brothers worked on the story for two years. Early versions focused on a plot involving twins who went to court to get a "divorce." The Polish brothers decided this was too untruthful, since they couldn't find any cases of Siamese twins failing to get along.

At the same time, they began working with a costume designer to see if they could create a believable physical fusion. Working with Michael's sketches, costume designer Bic Owen crafted a harness--a sort of double girdle--over which she sewed flesh-colored fabric. Only one scene in the film shows the twins' fused bodies unclothed, and it is fairly convincing. But even for the other scenes, the twins had to spend hours harnessed together.

Meanwhile, they did as much research as possible, interviewing medical experts, watching documentaries and reading everything they could find on the subject. They spoke to the doctor of a pair of conjoined girls who live in Culver City in Los Angeles, but decided they didn't want to meet the twins.

"We decided it would be better to respect their privacy," Michael says.

Hollywood was distinctly uninterested in the project, however. Agentless, the brothers showed the script around and got zero offers. When they tried to interest actresses in the role of Penny, they couldn't get past the talent agency clerks who read and reject hundreds of scripts a week. Top agents never called them back. At William Morris, they couldn't even get past the doorman.

Eventually they found funding through Joyce Schweickert, a wealthy supporter of the arts in Seattle; she more than made her money back on the sale to Sony Classics and foreign distributors. But when it was time to cast Penny, Michael--who directed, while Mark wrote most of the screenplay--insisted on an unknown actress.

"Everybody kept saying, 'You need a Parker Posey.' 'Who's popular in Europe?' " he recalls. "But we really wanted an unknown. It's so nice to start a movie with someone the audience could identify with, who had no 'famous' baggage, just their character's baggage."

They got their way, but the stress of the enterprise took its toll on them both. Each twin lost 20 pounds during the 17-day shoot.

Which is a scary thought; it is very, very hard to imagine the Polish brothers 20 pounds lighter than they are now. Both wear faded bluejeans (though Michael's are more shredded and holey) that barely cling to their wispy frames. They speak in low voices, rarely smiling. While they pick at their lunches--no, they don't order the same thing, and yes, they do eat--Michael tells their tale of a cross-border, working-class childhood.

The twins were born in El Centro, a border town near San Diego, to a Mexican mother and Montana-born father who flew cargo planes for the Navy. At age 7, they moved to a Sacramento suburb, a working-class town with one public school and a small-town sensibility. The twins were alike far more than they were not. They were artistically inclined; both liked to draw, but Michael had the more obvious gift for sketching and detail. Mark was drawn to acting and dance.

They were miserable students--D's and C's. Mark improved when he focused on the arts in his senior year, but he argued with his drama teacher when he insisted on mounting a stage production of "East of Eden" instead of "Bye, Bye Birdie." Similarly, Michael feuded with his art teacher and was kicked out of classes. They were 5-foot-3 and introverted, too shy to ask girls out.

Still, Michael was gifted enough to get a full scholarship to the prestigious California Institute of the Arts. After some acting classes in junior college, Mark joined his brother in Los Angeles and applied to Cal Arts, but didn't get in. So he sat in on his brother's classes and used Michael's college ID to go to the library.

He wanted to be an actor, but as months passed, the brothers decided they would make films together. Mark would write the scripts while Michael, the visually inclined, would direct. (His sensibility infuses "Twin Falls"--which has a bluish cast that grows lighter as the film progresses, and which consciously evokes the lonely urban-scapes of Edward Hopper.)

Waiting for a break in the movies, Mark worked as an extra, hanging close to the directors to soak up as much information as he could. On school breaks, the brothers would head up to Montana to help their father and older brother build a sprawling log house--which they say also helped shape them as filmmakers, teaching them to use blueprints and to plan carefully.

They made a couple of shorts, notably a film about Mexican boxing that won five prizes at festivals in the United States. Still, there was no interest from mainstream Hollywood. They wrote a feature called "North Fork" about a Montana town that suffers a flood when a river nearby is dammed, based on the true fate of a town their grandfather helped build. The story raised some interest, but no one was willing to let Michael, an unknown, direct, and Mark, another unknown, star.

Take Two

So they came up with "Twin Falls."

Rena Ronson, who became the producer, was struck after meeting the twins and hearing their pitch: These two, she thought, could pull it off.

"I was mesmerized by them just coming into my office," she recalls. "I've never met two people closer than them in my life."

On the set, watching the brothers work was almost eerie, Ronson says. Even strapped into the restrictive harness for hours, they didn't fight or become testy. If Ronson solicited the opinion of one, she didn't need to consult the other.

"It was extraordinary to watch. I've seen one get angry or frustrated at something and walk off the set, and the other will follow even if he doesn't know what's going on. They follow each other. They respect each other. They have an extraordinary ability to understand one another's emotions," she says.

"They really are 'one soul, two people'--that cliche really fits them."