YOU MIGHT HAVE heard the urban myth. An unwary business traveller has one drink too many and wakes up with a cracking hangover in a bathtub full of ice. The victim glances up and sees a note taped to the bathroom mirror: 'Call a doctor. You've just had a kidney removed.' As with all urban myths, the details change with the storyteller, but thanks to the wonders of modern technology, the basic story has been circulated from Saskatchewan to Shenzhen. Three or four years ago, when it was doing the e-mail rounds in Hong Kong, it caught the attention of scriptwriter Yeung Sin-ling and director Lo Chi-leung, who thought it could make the basis of an interesting horror movie. 'We tried to develop it as a story involving a man who kidnaps a woman, but we got stuck after the first couple of scenes,' says Lo. 'So, we put it to one side and made Inner Senses, instead. Then the head of Filmko [Alex Wong Hoi-fung] suggested the story should revolve around two girls and it suddenly became much easier to write.' The end result, Koma, is a psychological thriller starring two of Asia's hottest up-and-coming actresses, Lee Sin-je and Karena Lam Ka-yan. Eventually scripted by Susan Chan Suk-yin from a story by Yeung, the film is the second time Lo and Lam have worked together since Inner Senses, a finely crafted, atmospheric horror movie (and the last film made by Leslie Cheung Kwok-wing). Like Inner Senses, Koma derives as much of its impact from human drama and character development as from shocks and scares. But Lo says it's a very different film in terms of style and genre. 'Inner Senses was set in an old apartment building and had lots of scenes that were shot in the dark,' he says. 'This movie has many scary scenes in daylight and in public places. It's not a ghost story, it's a thriller. So, it's a bit more gory.' Although Koma starts with the organ theft story, it quickly evolves. Lee plays a society girl, Chi Ching, who's the only witness when a woman has her kidney stolen during a wedding reception at a glitzy hotel. Chi Ching picks Lam's character at an identity parade, but the police can't use her evidence because it turns out she has a motive for pointing the finger. Soon after, Lam's character rescues Chi Ching when she becomes the target of a vicious assault, and the two women - both outsiders in their own ways - become close, unaware that their friendship is dragging them towards danger. 'The entire film revolves around the relationship between these two girls,' says Lo. 'It's about jealousy and friendship. Sin-je's character is privileged and has people taking care of her, whereas Karena's character has grown up very poor, but she can still be envied for her courage. Girls have this strange ability to be extremely jealous of another girl but still be friends with her.' Because the film demands more of its leads than the ability to scream convincingly, it was essential to cast good actresses. Although relative newcomers, Lee and Lam have won several awards, and are renowned as princesses of the horror genre. Lee won the best actress award at the Hong Kong Film Awards and Taiwan's prestigious Golden Horse Awards, for her performance in the Pang brothers' horror flick The Eye. Lam won plaudits for her role in Inner Senses. Putting them together was a canny marketing hook by Filmko, which is financing the film. 'They're both great to work with, but quite different in their approach to acting and in real life,' says Lo. 'Sin-je is fairly straightforward, whereas Karena is much more complicated. She analyses everything. So, it turned out that they were a good fit for their characters.' Koma is only Lo's second scary movie, but he's already displayed his versatility in writing and directing on films as varied as comedy drama Viva Erotica (about a director who's forced to make a Category III movie), action thriller Double Tap and romantic comedy Fly Me to Polaris. He says he was first seduced by the film industry as a teenager, when he routinely skipped classes to go to the movies in Wan Chai. He started experimenting with 8mm cameras as soon as he left school. 'My sister [Carmen Leung] is a theatre actress who was always buying movie magazines,' says Lo. 'As a teenager, I read about many different kinds of cinema - mostly French, Italian and American.' Like many aspiring directors, Lo worked his way up through the ranks of the local industry, working as assistant director to the likes of Sammo Hung Kam-bo, Derek Yee Tung-sing and Clara Law Cheuk-yiu, before making his debut with Viva Erotica in 1996. He directed Double Tap in 2000, and has written the scripts for Daniel Lee Yau-kong's Moonlight Express and Jingle Ma Chor-sing's Hot War and Fly Me to Polaris. As Lo points out, all three of the movies he's previously directed starred Leslie Cheung, and he says he learnt a lot from him. They first worked together on Viva Erotica, in which Cheung played an idealistic director who has to deal with triad backers and a leading lady who won't do nude scenes. 'Everyone told me that, as a new director, it would be difficult working with a big star because they try to tell you what to do,' says Lo. 'But after three days, Leslie said to me, 'I trust you. Just do what you want to do'. I found that very encouraging. He taught me many things - especially about how to communicate with actors.' Lo says that during the shooting of Inner Senses - which touched on suicide and depression - Cheung's mood was as cheerful as ever, so he was unprepared for the actor's suicide last year. 'It was a huge shock for me,' he says. Lo is returning to comedy for his next project, Insect Girl, a special effects-laden fantasy for Emperor Motion Picture Group, which is due to star 16-year-old newcomer Isabella Leong. He's also attached to direct Jiang Shi, a horror movie for Michelle Yeoh Choo Kheng and Thomas Chung Choi-sze's Han Entertainment, and is developing The Classmates, about faded love and lost youth. 'I believe the future of the film industry here is very bright,' says Lo. 'Right now, Hong Kong movies have to serve several countries because the local market is dead - and that restricts the types of films we can make. But with the mainland opening up, there should be a lot more opportunity.' Koma will screen for the South China Morning Post Film Club on April 21, and will be followed with a talk by the director (in Cantonese). Contact firstname.lastname@example.org for more details. Koma opens on general release on April 22.