NEW YORK, NY.- Sitting in her dressing room last week at Irish Repertory Theater in Manhattan, talking about her latest role, actress Kate Mulgrew initially sounded like herself: an American from Iowa who happens to share a voice with Kathryn Janeway, the Starfleet captain she played on “Star Trek: Voyager.”

A minute or two into the interview, though, a Dublin accent started shading some of her phrases, and soon it was coloring all of them. That’s the first thing you need to know, because when you read her words here it helps to imagine their cadence as they hit the air.

The second thing to know is why she would slip into that lilt and sustain it for nearly an hour. She was simply holding tight to Beiv Scanlon, the character she is playing in Nancy Harris’ thriller “The Beacon,” on the Irish Rep main stage through Nov. 3.

Not that Mulgrew, 69, has been speaking with that accent constantly, but she has been doing it “a lot,” she said. “Yesterday I didn’t. I had to go off and do some things, and I didn’t want to disconcert people who’ve known me for years. Right? That would be odd.”

But if, offstage, the accent can be discombobulating even for those of us who don’t know her personally, it’s all in service of Beiv (rhymes with wave).

Woven through with sexual politics, “The Beacon” is a ghost story that’s also a murder mystery that’s also a domestic drama. Beiv, a transplant from Dublin living alone year-round on a rugged island off the coast of West Cork, is a famous feminist painter who has always put her work first, before her husband, when she was married, and their son.

“I know the kind of woman she is, insofar as she resides deeply in me,” Mulgrew said in her storyteller’s voice. “I’ve raised two sons myself. I know what the sacrifice is like and I know what it feels like, that harrowing feeling that there’s no way on Earth you’re going to accomplish all things well.”

She added: “It’s an impossible situation. So all my life, creatively, emotionally, I have walked a plank. And that’s what Beiv Scanlon does in this play. She’s walking a plank.”

For a decade the rumor has been that Beiv killed her ex-husband on the island, or in the ocean that surrounds it. Their grown son, Colm, wonders bitterly if that’s true. Might his father’s corpse, which was never found, be buried under the patio that Beiv is having built?

Charming when she cares to be, but with a knife blade glinting just beneath her facade, Beiv shrugs off the whispers. She knocks down the walls of her cottage and replaces them with windows, living as she chooses, letting the gossips peer right in.

At Irish Rep, in the empty upstairs rehearsal room, Harris mentioned that likable characters don’t interest her. Transgressive women like Beiv absolutely do.

“Even now,” Harris said, “it’s still not normal to see that kind of a character onstage in Ireland, or anywhere, really: somebody who’s sort of been a bad wife, a bad mother and a good artist.”

To her, Beiv’s baseline transgression is “her refusal to conform and behave.”

“It’s still shocking to have someone go, ‘I won’t be the good girl. I won’t play nice. I won’t make you feel better,’” she said.

Like the Irish theater itself, the main stage at Irish Rep has long been crowded with the work of male playwrights; female playwrights have been more of a scarcity.

But Harris is part of a changing tide. Born in Dublin in the 1980s, she wrote her thesis on catharsis at Trinity College Dublin, started her playwriting career in London and splits her time between the two cities. Her deconstructed romantic comedy, “Somewhere Out There You,” was seen a year ago at the Abbey Theater in Dublin.

She may be best known as the creator of the TV dramedy “The Dry,” which revolves around a newly sober alcoholic artist who leaves her London life to return to Dublin and her colorfully unhappy family of origin. (The first of its two completed seasons is streaming on Sundance Now.) In 2014, off-Broadway audiences saw Harris’ play “Our New Girl,” centered on a restless woman, who is married to a vain misogynist and unable to warm to her unnerving young son.

Then there is “The Beacon,” first staged by Garry Hynes’ Galway company, Druid, in 2019.

When Mulgrew’s manager called to urge her to read it, Mulgrew was in the midst of writing a novel. Called “The Irish House,” it’s a psychological thriller loosely based on the five years she spent living, on and off, in the west of Ireland.

She knows it’s a cliche to be the Irish American who swoons for the old country, but the place has always felt simpatico to her.

“When you think something’s in you, in your bones, then you test it,” she said. “And I went to Ireland and tested it for five years. It’s in my bloody bones. It’s almost like there’s a hollowness in the bones that’s filled with the steel and the want and the agony and the harrowing. And the bone marrow is composed of all of that stuff, you know?

“Whereas here your bone marrow is your bone marrow, and let’s go out and have another martini,” she continued, wryly. “But over there you’re working with the elements that threaten you at every turn, and at least in my case, just filled me with a longing, an unbearable longing. And Beiv has it, too.”

A 2008 Obie Award winner for playing Clytemnestra in Charles Mee’s “Iphigenia 2.0,” Mulgrew is drawn to tough characters, and to the primitive in Beiv: the sense that she is “dangerous, on the edge” and capable of practically anything.

Part of that primal ferocity is what Mulgrew is certain is Beiv’s love for her son.

“It’s wild love a mother has for her son,” Mulgrew said. “Mine’s wild, really quite shocking. It’s like, ‘Oh, really? Is that the bullet I’m supposed to take for you?’”

And, gazing into the imagined distance in her cramped dressing room, she stood up placidly from her chair and took a step toward the make-believe bullet, acting out a mother’s willingness.

Mulgrew is sure, too, that Beiv’s ex-husband is the reason she has moved to the island, whatever the truth of his death.

“She returns to the scene of the crime — to live,” Mulgrew said emphatically, and then switched tones on a dime. As if she were in the middle of telling a ghost story, she dropped her voice almost to a whisper: “Because people want to be near to their dead. I do.”

A pause, and even softer: “I do.” And again: “I do.”

All of this, still, in the Dublin accent — not method acting, nowhere close, yet flirting with the sort of extreme immersion in character that we tend to associate more with hard-core male actors.

For Mulgrew, it is what doing this role right demands of her, and so what if it’s unconventional. You get the sense that Beiv Scanlon would approve.

This article originally appeared in The New York Times.