Director Ang Lee and his young star, Wei Tang, talk about the steamy love scenes and sense of duty at the core of their Shanghai-set period piece of sociopolitical intrigue.

Taiwanese-born director Ang Lee doesn’t deny a greater sense of responsibility on his native-language films. While he ascribes to filmmaker Jean Renoir’s famous adage that all his films are his children, Lee admits that with these projects there’s a special level of involvement, exacting detail and anxiety, even, due to the additional scrutiny they receive in the Far East. “Doing an Asian film is like doing three Hollywood movies,” he says in a recent interview with Reelz. There is a sense that “each one is making history. I would need a long break in between if I were to do two back-to-back.”

Lee’s first film since Brokeback Mountain, and his first abroad since 2000’s Crouching Tiger, Hidden Dragon, is Lust, Caution. A wartime drama that shines a light on the clash of disparate forces and ethics — beauty and cruelty, desire and fidelity, personal awakening and patriotic duty — the movie is based on Eileen Chang’s short story of the same name, and co-adapted for the screen by Lee’s longtime collaborator, James Schamus. Part cloak-and-dagger tale of political espionage, part quite uncloaked tale of sexual release, the movie premiered to much chatter at this year’s Venice Film Festival, and earned a rare, if deserved, NC-17 rating for its aforementioned scenes of frenetic and not always pleasantly erotic coupling.

“I don’t know of any other modern day Chinese writer who is more revered and argued over than Eileen Chang,” says Lee. “And yet this short story is very different writing than her other works.” It was the opportunity to delve into female psychology and patriotism — two subjects not frequently explored within China, and even rarer still together — that most intrigued Lee, and made him want to tackle a filmic adaptation of Chang’s 46-page source material.

The film unfolds in Shanghai, and spans four or five years during the World War II Japanese occupation of the city. Unassuming Wong Chia Chi (newcomer Wei Tang) gets involved in a student drama club that also supports the resistance movement. As the troupe’s new leading lady, Wong sheds her shyness and finds liberation in slipping on the guise of another. The group’s plot to assassinate the head of the collaborationist secret service, Mr. Yee (Hong Kong-born veteran Tony Leung), calls on Wong to pose as the wife of a businessman, infiltrating Yee’s household by befriending his wife (Joan Chen) over card and tile games. While their first scheme goes awry, several years later Wong catches Yee’s eye and strikes up an affair, thus reviving the plot. Acting out pent-up aggressions and paranoia, Yee proves himself a sadistic lover. Yet Wong finds herself abandoned by the certainty of her youth, developing true if unlikely feelings for Yee in spite of his callous behavior.

Both because of this culturally incendiary subject matter and the fact that Lust, Caution hinges so completely on the young “mahjong Mata Hari” at the story’s center, Lee knew that he would have to find the right actress to play Wong. To that end, a huge search was undertaken. The winner, and perhaps a newly minted star: neophyte actress Wei Tang, then 27 years old, a recent graduate of Beijing’s Central Academy of Drama directing program and a former model and Miss Universe pageant runner-up.

Tang, dressed in a knit red dress, alternates between using a translator and speaking directly, but apart from an obviously restricted vocabulary and some occasional pronoun slippage, her accented English is for the most part direct and to the point — quite unlike her character, who is steeped in masked silences and uncertainty. A sly sense of humor even pokes through the cultural fog — “Oh, want to sleep?” she says when a reporter’s tape recorder tips over.

Tang details an exhaustive series of five auditions and call-backs, a process that she says was intimidating because of the idea of competing against “hundreds of other girls.” (In fact, Lee pegs the number even higher, saying that between he and his casting associates, 10,000 girls were seen.) After making it to the second round, Tang was granted an audience with Lee. “The second time I saw Ang, and we talked a lot,” she says, “all about my education, my family, my background and other things.” The Oscar-winning director’s filmography wasn’t one of those things, however; rather amazingly, Tang hadn’t seen any of Lee’s movies. “I just knew [he] was very nice, because I’d seen pictures,” she says with a sheepish grin, “And so I believed my feelings.”

For his part, Lee didn’t seem to mind Tang’s naivety or inexperience. If anything, he looked right through it. “When I saw [Wei] Tang,” he says, “I just thought, ‘She has the face of a Southern Chinese lady,’ which is what we needed. And when I met her, I could tell she had the temperament as well, to match the character of Wong Chia Chi.” By the end of the audition, it was clear to Lee that Tang had great potential to play the many different facets of the character — a woman who at once finds things within herself that she didn’t know existed even as she loses significant parts of herself. “I just looked at her and I believed in her,” Lee says.

And so it was then that the filmmaker broke the news to his actress, tempering the news of her having won the part with an explanation that he wanted the movie’s sex scenes to embody the rawness and desolation Wong felt inside. “At the last audition, Ang told me just that there were some explosive love scenes,” Tang says. “He didn’t tell me a lot. But I [didn’t] mind, I just wanted to try my best to express the character, because I knew that she’s very rich and I believed in Ang. So I said, ‘You can just tell me what to do.’”

“Of course, I felt a little nervous at the beginning,” Tang adds, “once we started filming. It was not something I was used to. But I just removed myself when the camera was rolling, I just lived the girl’s life. Wong is yearning for love. She’s a born actress, and can express herself better hiding behind this element of herself than any other way. And Ang and Tony were also so nice and supportive that I didn’t want to let them down.”

The pressure Lee felt to make a movie that was historically accurate, while also exploring new psychological terrain, seemingly rubbed off on his charges. “Wong’s passion was tremendous, but this movie was also so important,” says Tang. “It tells a story not often told.”

“The young actors in the film were learning about their grandparents’ China, which was touching to me,” Lee adds. “China has been through a lot, and things get lost. If this generation doesn’t connect with the past, which one will? We wanted to help make that happen. That was part of our mission.”