After contacting Chen and visiting her in Taipei, Mak set about adapting the story for the big screen, working with the novelist to transplant it from Taiwan to Hong Kong, and modifying some of the plotlines. However, the basic plot stays true to Chen's original work.

It tells the story of a schoolteacher, Butterfly, who is married with a small daughter and thinks she's perfectly content - until she runs into rebellious teenager Yip at a supermarket. Butterfly steps in to help Yip when she's caught shoplifting, and ends up falling in love with her. Eventually, Butterfly tells her husband about the affair and has to make a difficult choice between her lover and her family.

Although lesbian love affairs are probably not up there on the controversy scale with religious issues these days, Mak knew she had to tread carefully. The first hurdle was to find an actress willing to play Butterfly - ideally a recognisable name without which it would be difficult to raise finance. 'The casting was quite difficult because Hong Kong actors are not as open as in the US or Europe,' she says. 'Although I'm not doing any nude scenes or strong stuff, I still had to work hard to get the actors to trust me.'

Mak secured Josie Ho Chiu-yee, who she felt was perfect for the part and who was also supportive of independent filmmakers. Ho recently appeared in indie feature And Also the Eclipse. Mainland rock singer Tian Yuan was cast as Butterfly's lover, and Eric Kot Man-fai as her husband.

With Ho on board, it became easier to raise the rest of the budget. Hong Kong film company Filmko, which also has a history of backing new directors, has picked up most of the tab, and Mak has also applied for post-production funding from Europe.

Although the film is centred on a relationship, Mak says it's more than a love story, and has a message that should apply to many people, whether gay or straight. 'It's also about honesty to oneself,' says. 'Butterfly struggles between her family obligations and being true to herself. This theme can apply to everyone.

'I'm not a lesbian, but I find that when I'm struggling as an independent filmmaker, the only way I can continue is to try to be honest with myself. So, in some ways it's a story about me.'

Mak says she conducted research while writing the script by holding discussion groups with young lesbians. One of the strongest issues to emerge was that, although many heterosexuals in Hong Kong may claim to accept same-sex relationships, this changes if they discover that someone in their own family is gay. 'From the family point of view, young gay people still face many obstacles and find it difficult coming out to their parents,' says Mak. 'I've tried to put a sense of this into the film because we're still very conservative on this issue. We may claim to be tolerant, but that's not the real story.'

The film is scheduled to wrap this month, and Mak plans to submit it to international film festivals. Her first feature, Brother - a road movie about a young man from Hong Kong searching for his older brother on the mainland - won a prize at the Venice Film Festival in 2001, so she hopes she can return there.

'Film festivals are the only route for independent filmmakers in Hong Kong,' she says. 'They enable you to make some noise that may help the local box office. Otherwise, nobody will go to see your film.'