The bewildered eponymous central character of The Mai is not a warrior; she has built a house in a desperate attempt to win back a man incapable of loyalty. The haunted Portia Coughlan and Hester in By the Bog of Cats represent two halves of the one sphere. "Yes that is true. Portia is beset by the internal, whereas Hester is defeated by the external, although she also has some responsibility." Also, in the case of Hester, she is the definitive outsider. "I choose to make her a traveller because travellers are our national outsiders aren't they?"

The landscape is also vital to both plays as well as to both characters. For Hester it is the bog, while for Portia the Belmont River has come to dominate her life, admittedly for reasons far beyond the allure of local geography: "I never knew that river but I always liked the name. I don't see the work as autobiographical at all because it's not. It comes from the imagination, stories I've heard, the odd things people say."

Landscape for Carr, though so vividly physical by allusion in the plays, seems suspended between memory and imagination. "Landscape," she pauses, as if weighing the word, "is another character - if you can get it right. It needs to be present, to have a presence. But if you labour it too much it can be overly symbolic and self-conscious. Get it right, though, and it can add a subtle layer."

The flat midlands countryside with its expanse of bog and undulating stretches of canal has a subtle, underestimated beauty of its own; it also has a topographical diversity dramatically represented by the Slieve Bloom Mountains which unexpectedly dominate the county and are well worth investigating. At the mention of a mysterious local passage over the mountain, known to her as The Cut, Carr's face lights up and she pronounces the word as the locals do, with a mute "T".

Long resident in cities, which she says she loves, Carr remains a countrywoman and agrees that bogs are fascinating places. Boora Bog, a couple of miles from her family home was a fine playground. "When you're out on the bog, especially where its been cut for the turf, you could as easily be on the moon. They're amazing places, especially at night." The dead such as The Ghost Fancier walk freely in her plays and it is understandable considering the ghosts who have long lain preserved in the bog.

Bogs preserve as well as contain or conceal. Carr mentions the wealth of archaeological treasures found in them, particularly in the Co Offaly portions of the Bog of Allen, the bull artefacts of the Dowris Hoard which in turn gave its name to a phase of the Bronze Age. "There's a Greek quality to this as well as being very Celtic."

Does she believe in ghosts? "I believe in them as physical presences and I also believe in the role they play in dreams. There are certain characters who appear and reappear; it's like another relationship."

Was she born in Tullamore? "No, Dublin," and on hearing my disappointment adds, "I was immediately brought to Offaly." She was raised at Pallas Lake ("a lake not a village") about seven miles west of Tullamore and is the second child of six. "I have one sister and four brothers. My mother was the principal of the local national school and my father was a civil servant."

At home the Carr children built a theatre in a shed: "We wrote plays and acted in them. Our friends were the audience." In the introduction she wrote for the Faber edition of her plays she recalls, " . . . our dramas were strange and free and cruel . . . We loved the havoc, the badness, the blood spillage, but loved equally restoring some sort of botched order and harmony. Ignorantly we had hit upon the first and last principles of dramatic art."

From Gort Na Mona National School where her mother taught her - "it was fine, she was a huge influence on me. We were very close" - Carr went to the Sacred Heart Convent in Tullamore. For the final three years leading to the Leaving Cert she attended Presentation College in Mountmellick as a border.

"I think it was because my mother thought we weren't studying hard enough. She was big into education and used to tell us: `You'll have to work hard. I've no land to leave you.' " But Carr always did well. "I loved English, but I was also good at Biology and Economics." She laughs as if this is evidence of eccentricity. "I can still do a demand and supply curve."

While at school she also continued writing plays. "I always wrote the Christmas play," she says, and it seems unnecessary to ask if they were unconventional: "Well, they were never about Christmas." Her childhood and youth were happy. Her mother's death, some five months before Carr sat the Leaving Cert, remains a huge loss. "You never get over losing your mother that young; she was only 43."

On leaving school Carr went to University College Dublin to study English and Philosophy. While there she particularly enjoyed philosophy: "Kant, Derrida the deconstructionist - for us he was a philosopher as well as a literary critic - it was an intellectual trip, but it was also fascinating, a whole new thing. I also loved reading Plato, I can still remember the Theory of the Forms. I've forgotten most of the rest but then it was a long time ago."

She also joined Dram Soc, quickly discovering she was not a performer. "I kept forgetting my lines, but I could remember everyone else's." She casually mentions two abortive attempts at MAs, one in Anglo Irish literature, looking towards Beckett, and later "I was going to do one in film studies but well, it never got going."

False notes in writing irritate her and she is honest about flaws in her own work. Even of The Mai, she can pinpoint the exact moment of weakness. For her this is when the writer's ego intrudes. "When you come in and say something that's off, because you're unsure, not convinced yourself and something is added that is you, not the play."

Of her first play Ullaloo which was produced at the Peacock, she says, "let's not talk about that . . . let's forget it. It opened, it came off a few days later. I was trying to be very Beckettian. One of the characters was involved in growing his toenails and the other did nothing." Certainly Beckettian is her hilarious second play Low in the Dark first performed in 1989. It has great fun with notions of sexuality, its role reversals and its expectations. As one of the characters proclaims "I want a woman who knows how to love. I want laser beams coming out of her eyes when I enter the room. I want her to knit like one possessed. I want her to cook softly."

Each play has for Carr represented a new level of learning. Her dialogue has become terser. Many of her characters converse in the shorthand used by people who know each other too well to waste words. There are no long speeches, no fake poetry. Even at its most bizarre her work is realistic. Carr is a writer who listens. Asked about her feelings towards her plays to date, she at first seems quite detached and says, "Once they are done, I tend to move on," but having thought about it she remarks on the new excitement which returns when a play is performed, or a new production is prepared. "There is great joy in seeing a play take shape."

This response reflects her attitude to character, does she think of a character in terms of performance or of a personality developing? "Definitely a personality developing." It is interesting the way love, often desperate love as in The Mai, is the true theme of her work. "It is difficult. Irish writers don't write that well about love, except for McGahern."

Increasingly drawn to prose, she says she is fascinated by the novel. Though a Hennessy short story winner in 1994, she sees herself as an apprentice prose writer. "I'm a playwright who would love to write short stories."

The Druid/Royal Court co-production of On Raftery's Hill by Marina Carr is at the Town Hall Theatre, Galway, May 9th-13th, previewing from May 5th; at the Gate Theatre, Dublin, May 25th-June 26th; and at the Royal Court Theatre, London, June 29th-July 29th. It is also part of "The Island: Arts From Ireland" at the Kennedy Centre in Washington DC May 18th-21st.