'If I'm the only one who thinks that, or one of the handful, it makes me abnormal. But if everybody wants it, does that make it normal? Does that make it moral?'

Ng says it is especially painful for dancers to see their bodies deteriorate over time and the idea of preserving them at the height of perfection may seem tempting. The murderer may thus be doing good by preserving his victims' beauty, even as he takes away their lives.

'What if the other person believes in what you are saying? If they say 'OK, I want eternal beauty - so let me give my head to you and this will stayforever'.'

Described as a 'murder mystery', Love on Sale combines this idea with a new take on Kurt Weill's 1933 Seven Deadly Sins to examine the theme of obsession and what constitutes sin.

Weill's work is a sung ballet with a satirical libretto by Berthold Brecht in which two sisters, Anna I (who sings) and Anna II (who dances), spend seven years labouring in the city in order to build their family the 'little house in Louisiana' they long for.

They encounter one by one the medieval deadly sins of lust, gluttony, greed, sloth, wrath, envy and pride. In Brecht and Weill's cynical treatment, right and wrong are turned on their heads as the innocent Anna II sacrifices her own needs and commits all seven sins to fulfil her duty to her family.

Asked if he feels that in today's Hong Kong sins are also considered virtues, Ng says: 'It's not necessarily that a sin is a virtue, but that we're too numb to tell the difference.'

Despite this bleak view, he is adamant that he is not using Love on Sale as a soapbox. 'Who am I to warn people that they're doing wrong? I resent that - telling the world they're wrong, it gives me the shivers. I am just warning myself.'

Ng has incorporated Ute Lemper's celebrated recording of Weill's piece into the score but is not following the storyline although he has retained the idea of 'Anna' (there are now 14 instead of two) and the sins.

Each dancer represents one of the body parts that a central figure, played by singer Chu Pak-him, is seeking to collect.

Ng describes Chu's role as 'an agent trying to connect these body parts together. He's a salesman, too. He's trying to convince people to take up certain things, to fall into a trap, to fall into his arms.'

Ng hit on the idea of using Chu after hearing him perform in a local adaptation of Stephen Sondheim's Sunday in the Park with George. 'I immediately connected the murderer with someone who wants to own something, who is desperate for something, out of need, out of desire. It's all in his voice. Musically, as a sound, it's exactly what I'm looking for.'

Chu will speak, not sing, but Ng says that although there will be information in the words, his voice is treated as music: 'If you don't understand a word, it's fine, it won't deter you, like Chinese people may not understand the German text [of Seven Deadly Sins].

'That's why I chose the Ute Lemper version, because the quality of her voice is a message in itself.'

Chu is writing his own words and putting his own ideas into the show. He will not dance but will be on stage the whole time, interacting with the dancers.

Another key collaborator is Stanley Wong Ping-pui, better known as anothermountainman. In addition to a successful career in advertising, Wong is an artist, photographer and film director.

He designed the show's controversial publicity leaflet and is responsible for its startling photos of different parts of the dancers' bodies (shown naked, although the show itself has no nudity). Wong is also creating the set.

'[Wong] proposed a colour and sold the idea to me,' says Ng. 'It's the blue that is used for special effects, a blue screen to convey the concept of invisibility.'

Ng says 'obsession is to fill a need, fill a void ... I'm filling this emptiness. That's why I make work.'

At first glance a murderer's obsessive desire to collect body parts has little in common with the need to create art but Ng feels there is a very big similarity. 'In order to finish this artwork, I can take a lot out of people. Some are willing, some are not.'

This reflects Ng's method of asking his collaborators to share in the creation of the work, so it becomes something that has meaning for them as individuals.

'I keep asking them questions and they have to give me an answer, give themselves an answer. They should not just be machines, just doing what Yuri says ... They have to think and to challenge me a little - if they dare, if they want to, they should.'

As part of this process, Ng has spent time studying each dancer's body language and identifying the body part they will represent.

'We asked them to find the part of the body that is strongest, that is unique. Like Dominic Wong's mouth. So he has to use a lot of lips.'

Ng is also employing a strong element of improvisation, which will be part of the performances. This is a bold move but Ng feels the CCDC's dancers have the experience to make it effective. Another unusual aspect of this production is that there will be seven performances - the longest run the company has ever done.

Ng says the venue is small so attendance may be no higher than for two or three appearances elsewhere. However, doing the show more times is important because 'it's an opportunity to let the work develop. If the company can afford to develop it once it gets to the stage, I wish more companies would strive for that, not just for ticket sales.'

Despite the dark underlying themes, Ng says Love on Sale will be 'a lot of fun, I hope. Because I'm having fun with it. It should not look profound.'

There will be plenty of what Ng calls razzle-dazzle, including male dancers imitating Marilyn Monroe and costumes made of plastic bananas.

'The bottom line is you will enjoy it.' There may also be a surprise at the start. 'Make sure you get there on time,' warns Ng. 'I'm not going to give anything away, but don't come late.'

Love on Sale, HK Cultural Centre Studio Theatre, TST, Fri-Sept 28, Sept 30, 8pm; Sat-Sept 28, Oct 1, 3pm; HK$160-HK$200. Inquiries: 2329 7803