Meet the Watermans. Gail works as a receptionist at a local hospital in Glasgow. She has nine-year-old twins and an 11-year-old daughter, Lauren, who loves dancing. Her father, Robert Kelly, is a retired finance manager who devotes his spare time to collecting books on Scotland. Her mother, Patricia, a nurse, is also retired but continues to work at the hospital one day a week. The family live together in the same house near Hampden Park and particularly enjoy throwing impromptu parties with the karoke machine. And for seven nights in October, you, the public, are invited to join them.
The Waterman family are the subject of Butterfly, a new piece from the Quarantine theatre company, which, since it was set up by Richard Gregory and Renny O'Shea in 1998, has thrived on using ordinary people to explore the relationship between truth and artifice within theatre. Butterfly will take the form of a party thrown by the Watermans, with real food, music and a paying bar. The Watermans will be "on stage" among the audience, playing themselves, swapping stories, chatting to one another, arguing, as families do. No one is quite sure yet what is going to happen.
The process began when Gregory placed flyers around Glasgow's museums and libraries, asking for a family spanning three generations to get in touch. "We needed the entire family to commit for at least two months to a piece of theatre that would dig beneath the surface of who they were," says Gregory. "Perhaps unsurprisingly, we got only about six responses." The flyer caught Gail's eye on the last day for applications, and she emailed Gregory immediately. "I thought: why not?"
Butterfly will have been extensively workshopped by the time it reaches the stage, but the essence of it - the lives of the Waterman family, who they are and the emotional dynamics between them - is absolutely what will appear before the audience. None of them has any previous experience of acting, although they all love the theatre and go to musicals together quite a lot. The point is, of course, they won't be acting. "We're just being us," Lauren says. "There's nothing to be nervous about."
If it sounds a little like reality TV transposed to the stage, it's fair to say that Butterfly shares with programmes such as Big Brother a commitment to using the stuff of real life directly to illustrate the extraordinary within the ordinary. While Charles Bell, who, as arts development manager at Glasgow City Council, oversees programming at Tramway, agrees that reality TV provides an accessible starting-point for Butterfly audiences, for Gregory the similarities end there. "Quarantine is simply part of a long, 30- or 40-year tradition, since the 1960s, of artists looking at themselves as the starting-point for a creative process rather than looking to the outside world," he says. "We still use the metaphorical language of theatre - music, movement, images etc - to give our stories the sort of impact that simply watching a slice of real life would never have."
Quarantine's defining interest in closing the gap between performer and material has given it an impressive reputation for theatre that radically dismantles the conventions by which we normally experience it. Bell says that Quarantine take the notion of the performer to an extreme, not least because the performer is also very much part of the audience, and frequently a member of the same local community. Quarantine's first Tramway show, See-Saw, took place within the audience rather than on stage in front of it, using a mix of professional actors and members from Glasgow, from an eight-week-old baby to a 75-year-old woman, some of whom appeared as ordinary members of the public outside the theatre before the show. EatEat, produced last year at Leicester Haymarket, used refugees to tell autobiographical stories over a meal eaten with the audience. And in the highly acclaimed White Trash, at the Contact Theatre, Manchester, earlier this year, seven white, male, working-class, non-professional actors, again from Manchester, swapped uncomfortable personal stories of unemployment, racism and prejudice around a pool table.
The process is, by definition, high risk. At the start of rehearsals, no one, least of all Gregory, has any idea what the final outcome will be. "Quarantine doesn't give itself much of a safety net," Bell says.
Gregory agrees. "I may fall flat on my face one of these days," he says, "but that doesn't worry me. I set up Quarantine [he used to be an associate director with the Northern Stage theatre company] because I wanted to get out of an environment where risks weren't really present. For me, theatre has take us to places where we might just see the world in a different way and to do that, we have to push ourselves beyond what we already know."
It might be tempting to see Quarantine's work, with its emphasis on the authenticity of the performance, as possessing a similar journalistic authority to the verbatim theatre of Nicholas Kent's Tribunal plays at London's Tricycle, and recent plays by David Hare, both of which source material directly from testimonies given by members of the public. Instead, Quarantine's work is, perversely, both more real and more theatrical.
One of Gregory's early influences was the work of the Belgian director Alain Platel, whom he describes as "bringing high art and low art together in a great, chaotic, incredibly moving mess. You can feel the material is incredibly closely connected; there's a rough human beauty about it." He aims to produce a similar effect through his own work. "I start with a set of questions I want to explore - in this instance, what family means to us. Then I set about finding the form. The material is taken from the Waterman family's response to exercises undertaken in the rehearsal room."
It's a largely confessional process: Robert Kelly, for example, admits that he will be telling his wife little things about himself that he is quite sure she doesn't know.
"Sometimes things can emerge in a controlled way; sometimes entirely accidentally," Gregory continues, emphasising that no one is obliged to talk about anything they don't want to. "We use a lot of choreography and music as well as text. I like the fact that the values of high art and a formally imagined theatrical framework can sit alongside something that is raw and potentially incomplete, with moments that can look entirely spontaneous."
Quarantine acquires its theatrical conviction from the fact that, unlike in most theatre, the actors are able to insist on the truth of their own performance. Inevitably, too, the work initiates a heightened sense of self-awareness. Kelly admits that Butterfly has "made me more aware of my past and where I'm going with my future. I've never linked the two in quite this way before."
Harley, 23, one of the actors in White Trash, found the process an even more concrete process of self-definition. "I had never thought about who I was before."
And what of the audience? Quarantine makes them witness to the lives of real people in a highly theatrical framework, in a way other theatre does not. "People will take what they want from it," Kelly says. "But, basically, Butterfly will make them think about themselves and their own family in the same way it has made us think too."
'Butterfly', Tramway, Glasgow (0845 330 3501; www.tramway.org) 7 to 9 and 13 to 16 October