Prepare to be amazed and not a little shocked ...

for currently living and working in the basement warren of rooms at Summerhall, Edinburgh, is a scientist who maintains "children should be seen and not heard." And would you believe? He practises what he preaches. His professional name is Dr Broderick MacKenzie, but we will come to know him as The Voice Thief - which just happens to be the title of the new Catherine Wheels show for families and youngsters aged nine and over.

Luckily, he has not been experimenting on the company's director, Gill Robertson, so she is able to fill in some of the scary details - without giving away too many of the secrets being put in place for the promenade through the reclusive doctor's domain.

It seems this rarely seen character was born with hyper-sensitive hearing. All noise affects him but the shrill, high-pitched voices of girls, especially, cause him such physical pain and misery that he has been driven to silence them by spiriting away their powers of speech, and sealing them into glass jars. His wife has fallen victim to his arcane procedures, and now his 17-year-old daughter looks as if she too is a likely candidate. Maybe best not to scream, then, when you visit his laboratory in the Institute Of Vocal Harmony.

"When you start to talk about women being denied the freedom of speech, it becomes very dark and frightening," says Robertson. "And if we were doing a show for adults, we would go there. We would look at the societies all across the world where women do not have a voice in the decision-making, whether it is at a government level or even in their homes.

"But this is a show for families and really for children, so that puts the brake on the darkness levels - not totally, but we are making it more like one of those scary fairy-tales where you know it is not real, but somehow you do wonder if it could happen ... to somebody else, of course!"

In fact, the idea of a voice thief who targets women has been gathering momentum in Robertson's mind for a while now, ever since she took part in a month-long workshop project run by award-winning artist, Mark Storor in London. Storor's work occupies a space between live art and theatre: it is devised, often site-specific and always collaborative. For Robertson, it was another part of the learning curve that she has stayed on, despite Catherine Wheels being hailed as one of the UK's leading theatre companies for children and young people.

"It is about being curious, staying curious," she says. However, not everyone who has already hailed as being at the top of their game does go off, in learner-mode, with an open mind and an interest in different creative processes.

For Robertson, this kind of stimulus and research is clearly tied into her approach to making work for young audiences. A cut-down version of a show for adults will not cut the mustard for a nine-year old who is techno-savvy, clued up on Doctor Who or an avid follower - maybe not just on screens but in print - of the sci-fi fantasies they can recreate with their own Lego kits.

"I really do not want, ever, for children to come into a space and be told they 'must behave' - which really means sit down and shut up. I want our audiences to have fun, maybe go away thinking about what they saw, and putting together their own ideas about it - and if these get discussed later in classrooms, that is great.

"But even if you give them the freedom to respond, you still have to create a structure for them to follow. If you have decided your show is going to be a promenade, the fear is the story will get lost as they move from room to room. It has been a challenge and we will not know how - or if - it is working until we bring in a couple of schools for test runs. We might have to adapt and change things at the very last minute."

Well might she laugh as she says this. Last-minute changes are not unknown. There is the time when the Witch in Catherine Wheels' memorable Hansel And Gretel was injured and Robertson found herself on stage, in full scary kit and cackle, looking for juicy children to oven roast. Hansel And Gretel was first staged as the East Lothian part of the National Theatre of Scotland's inaugural, nationwide project, Home. The production was so successful it came indoors from the woods at Prestongrange and subsequently won Best Children's Show and Best Design at the Critics Awards For Theatre In Scotland 2006.

According to Robertson, however, The Voice Thief is turning into a much more complicated promenade than Hansel And Gretel.

"That is partly because with Hansel and Gretel most people already knew the story," she says "and at Prestongrange, they were having to walk through the dark, along muddy paths in the woods, so they focussed on that until they saw the Witch's house. Here, in the basement, we have got eight different rooms along a narrow corridor and we have had to make sure the rooms do not just become a diversion. They have to feed into the story, right from the start when you go into the 'decontamination' area - just to make sure you are not bringing any bad noises with you - through to when, just like Dr MacKenzie's daughter, you realise what he is planning to do next."

Robertson reckons that what designer Karen Tennent is intending to put in this particular room - apparently a dentist's chair has been mentioned - will spur most young imaginations to a grim conclusion. Those of a nervous disposition might even sidle towards the exit, but never fear, the doctor's daughter has been discovering there is a misguided, even monstrous side to her beloved father she cannot ignore.

"It is, again, about women being able to stand up for themselves," says Robertson. "But actually, the journey a heroine makes is, I think, a really interesting one for boys to see and understand as well. And adults, because it is not the biff-bang-wallop 'you battle the baddie' plot, it is more about finding your way through dangers, maybe with the help of others, and by being able to ask for their help. It is about finding yourself in the process. It is not about riches, or power, or even about winning. It is about being brave enough to do what is right for everybody. For all those voices trapped in the jars, because they have a right to be heard."

Down in the Summerhall basement, the noise of last-minute hammering and sound checks would probably drive Dr Broderick MacKenzie crazy. For Robertson and her creative team, the hopes are that, in The Voice Thief, they have devised a very special Big Adventure where the scary strangeness will be magical and funny.

"A bit like Willy Wonka's incredible factory," says Robertson "but without the mega-budget and the Oompaloompas. It is such a privilege to have all this space, and to be able to turn the rooms into thrilling experiences for the unsuspecting audiences who walk down the stairs."

And if they leave wide-eyed and lost for words, Robertson will know The Voice Thief has given them something to talk about, once they are out of his earshot!

The Voice Thief is at Summerhall, Edinburgh, from Nov 1-15.

Times vary: details from www.catherinewheels.co.uk