Selina Cartmell's bold ideas have raised eyebrows. If you don't have a dark side, you can't experience the light, she tells Peter Crawley

It was just a minor crisis, Selina Cartmell explains with a small, self-deprecating shrug; the kind of thing you go through at a certain age. A sudden case of stage fright, brought on in a theatre in Glasgow, it eventually resolved, through tears and recriminations, into a personal epiphany: that she should become a director. Most people, en route to discovering their place in the world, will have such a crisis. "Mine just happened to be getting raped by a man in a mask," she says.

Perhaps we should explain.

Cartmell's conversation, much like her theatre, tends to be fluent and involving, laced with dark undertones and sudden, unexpected jolts. A striking young woman in a black leather jacket, with short twists of plum-coloured hair, Cartmell's soft home-counties accent makes an attractive impression: two parts English Rose to one part Goth. As a postgraduate student, Cartmell attended Glasgow University with hopes of becoming an actor, until she found herself on a stage, mentally compiling a shopping list, while she was symbolically raped - by a man in a mask - in a well-received piece of abstract nonsense. She felt like a fake.

"I thought, this is such a con," she recalls. "And then I got terrible stage fright and decided, 'that's the director's fault'. A director has a lot to answer for, on many levels, and one of them is obviously working with actors. I always felt frustrated as an actor, because I had my own ideas, and I thought they were okay ideas, and they should be looked at."

These days, more and more people are looking at Cartmell's ideas. In the three short years since she founded Siren Productions, her darkly compelling aesthetic has made an impression on independent Irish theatre.

From devised pieces such as La Musica, the dance piece Shutter, and the absurdist fable of Fando & Lis, to her work with the boldly experimental Operating Theatre Company, Cartmell's stage abounds with ideas from the theatre of the absurd, from fairytale, from dance, opera and classical theatre. On more than one occasion, reviewers have invoked Alice Through the Looking Glass in either admiration or bewilderment. (In fact, her first production in Ireland was an off-the-wall adaptation of Alice in Wonderland, staged in 1996 while she studied for a year in Trinity College.)

Last year, however, with Siren's astonishing production of Titus Andronicus in the Project Arts Centre, Cartmell's burgeoning career reached its tipping point. Winning four Irish Times Theatre Awards, including Best Director and Best Production, Cartmell had staged an epic on a shoestring, taking one of Shakespeare's earliest and least revered plays, and realising it with the spectacle and pulse of a fantastic opera, by turns sordid and beautiful. For independent theatre, it was a triumph of the underdog.

Cartmell now walks among the overdogs - in talks with the Abbey and currently directing Catastrophe, one of Samuel Beckett's final and most political works, at the invitation of the Gate Theatre. "I do find it strange," she admits, "because two or three years ago I would probably not see myself working in this environment."

It would be easy to think that the strictures of Beckett's drama represent something of a strait-jacket for the creative director, but Cartmell disagrees. "Initially, whenever I read a text, I go through a period of unlocking my way through it. It's the same with Catastrophe. I'm trying to find a way that I can approach it that interests me and that hopefully will interest the actors without changing anything radically with Beckett's work. The beauty of Beckett's work is the simplicity of it and keeping him pure."

Cartmell, who once wrote a dissertation on Japanese Noh Theatre and Samuel Beckett, doesn't immediately strike you as an authority on theatrical purity. Her career thus far, she says, has been guided by "the three Bs": Barker, Beckett and Berkoff. It's an unholy trinity known to many a theatre student, but Cartmell tends to speak of such disparate icons and theatre styles as though they are intimately related - not figures separated by time and place, but ones that seem to break open and emerge from each other, like a series of Russian Dolls. Can she persevere with such a vision as she enters the Establishment?

"What I'd love to feel one day . . . " she begins, "and all my big idols do this; they straddle opera, theatre and film, and they do it incredibly successfully and in such a way that they never lose any integrity."

Julie Taymor, who staged and filmed Titus, is one such an idol. "So it's just to find a place where you're truthful, whatever the circumstances are."

She agrees that Titus, which, in its more restrained moments, involves gang rape, mutilation and mother-son cannibalism, is not the obvious choice for such truthfulness. "The thing that always got me going about it," she says, "is that I love the ambition of Shakespeare when he's writing at the time. The total embracing of absolutely everything he could possibly get into the play. And I felt challenged by that. I really enjoy working on that epic scale as well. Working with all those wonderful, creative people and actors in a way that was collaborative on many levels. People say it's the worst Shakespeare. I disagree. I don't think it is. I think it's actually a very beautiful story. So I'm very interested to try to question what everyone thinks. To maybe dig a little deeper: It doesn't have to be like that; it could be like this."

Born in Buckinghamshire, brought up in Cumbria, educated in Somerset, London, Glasgow and Dublin, Cartmell seems most stimulated when in a state of flux. "My most formative time was when I was in Bali and Hong Kong travelling," she recalls. "That's usually the time when I absorb and pick up a lot of things, and I think I always saw the world ever so slightly differently anyway."

In an article she once wrote for Irish Theatre Magazine, Cartmell articulated a philosophy in which all boundaries between theatre and the everyday world dissolved, in which none reigned supreme: writer, director or actor. "What if we were all there in the rehearsal room for each other?" she wrote.

Today she elaborates on that spirit of collaboration. "If you create that working environment," she says, "you can allow actors to go with their instincts. Because, most of the time, their instincts are far better than yours. You respond to them, and they respond to you, and most of time you come up with something that works for you both. You hope that you create that connection together. It's the whole art and life thing; all these actors bring so much of their lives into a piece of work. In terms of casting - and the casting took ages for Titus - I'm interested to find out a little bit about them and where they're at, for both our sakes, to find out if it's something that they want to do."

This has lead her to work with a company of like-minded people - Catastrophe, for instance, features her leads from Titus, Owen Roe and Olwen Fouéré, and she has just returned from a residency in Paris working with Fouéré on The Gospel According to Judas, a monologue written for the actress by Frank McGuinness.

"I don't know if I'm that intense," she says. "But when I'm working I am intense; I live and breathe and sleep it. I call it the curse. It's the curse when you're doing the work." She pauses and her tone pivots toward the upbeat. "But it's a good curse." Those she works with, she thinks, "already have the curse. And maybe that's the connection."

In a theatre culture where the director has traditionally been seen more as facilitator than creator, more manager than artist, Cartmell is a breath of fresh air. Speaking with unusual candour about her "curse", she will admit that she is present in all her work - and in the velvety darkness of Alice in Wonderland especially.

"I think there's a lot of me in that,," she says. "How so? I think probably the madness in it. I think there's always an element of that dark madness in my work. The surreal element. It's always been a part of me I think."

Later she describes her next production for Siren - a site-specific work inspired by missing women in Ireland called Scene of the Crime - as "macabre, dark and surreal." What keeps drawing her toward this world? "Everything about it," she says, and her eyebrow arches a little conspiratorially. "I love it. I just think that's where we live our lives. And the flip side of it is that we live our lives with lots of laughter. But if you don't have that dark side, you can't experience the light."

As Cartmell graduates from the fringe, some of her admirers worry that her sense of iconoclasm and irreverence could become diluted. However, if her casting for the tyrannical role of the Director in Catastrophe is anything to go by, Cartmell is not easily cowed. At first she considered George Galloway for the part, but then she entertained another idea. "I actually said to Michael Colgan, 'You should do it'." She stops to weigh his credentials. "He has the cigar," she smiles. "He'd be fantastic."

• Catastrophe runs from tonight till Sat at the Gate, as part of the Beckett Festival