Kelly Macdonald hits right combination on ‘Boardwalk Empire’

Kelly Macdonald’s character on “Boardwalk Empire” — the Irish immigrant-turned-grande-dame Margaret Schroeder — would fit in perfectly at Manhattan’s Bowery Hotel. The dimly lighted, 1920s-style lobby, thick with antique furniture and copious crushed velvet, easily conjures the shady backroom politics, gangster showdowns and whorehouse rendezvous of the show’s Prohibition-era Atlantic City.

Sitting in the hotel’s restaurant, however, the 35-year-old Glasgow native practically blends into the background. Soft-spoken verging on shy, she wears a plain gray T-shirt and no makeup. Her honeyed hair falling messily around her shoulders, Macdonald looks more like a laid-back grad student than a TV star, incognito, on her day off.

Over the past decade and a half, Macdonald has appeared in more than two dozen films and TV shows in the U.K. and stateside. She’s poured herself so completely into her many high-profile but humble roles — like that of Texas trailer park wife Carla Jean in “No Country for Old Men,” an aristocrat’s servant in “Gosford Park,” mousy kitchen maid Evangeline in “Nanny McPhee” and the ethereal ghost of Helena Ravenclaw in “Harry Potter and the Deathly Hallows — Part 2” — that she never emerged as a star in her own right, a Hollywood brand. Which is how she prefers it.

“I get recognized at home a little bit in Scotland, because it’s a small place. But it was never really a thing that happened here,” she says with a sing-songy lilt. “Now it’s more of a thing. Kinda weird. I don’t like it.”

Macdonald’s career has percolated, quietly, rather than taken off — lingering at cult-level status, despite plenty of critical acclaim. In 2006 she won an Emmy for her spirited performance in “The Girl in the Café.” Now, as the second season of “Boardwalk” gets set to premiere Sunday and with an Emmy nomination for her work on the show, Macdonald may soon cross the threshold into household name territory. In HBO’s billboards and advertisements for Season 2 plastered across Los Angeles, Macdonald looms prominently beside Steve Buscemi, glamorous and larger than life.

“It’s always been slow and steady, my career trajectory,” she says. “This feels like a definite turning point.”

Her role in “Boardwalk” — a battered wife turned poor, widowed shop girl initially — was familiar ground to Macdonald, who has a history of playing women of service or struggle. Not far into “Boardwalk’s” first season, though, the character of Margaret takes a few sharp turns and finds herself quietly, unexpectedly wielding power. She is now Nucky Thompson’s mistress, reining over a household of servants as well as keeping a sharp eye on the political machinations around her, poised to save Nucky’s skin and safeguard their cobbled-together family.

Margaret’s steep and twisting character arc — played with expert, nuanced touches — makes her easily one of the show’s most complex and arresting characters alongside Steve Buscemi’s surprisingly kind gangster, Nucky.

Her character’s circuitous journey was as much a surprise for Macdonald, week to week, as for the audience. She typically didn’t get scripts far in advance, she says. “From the pilot, I thought I knew who she was and kinda based everything around that. And then I had to change.”

The 360-degree turn was intentional, according to “Boardwalk” creator Terence Winter. Part of why he cast Macdonald in the first place was so that the show’s writers could flip her familiar image on its head.

“Margaret is a character I knew would initially be perceived as a sort of saintly widow. We wanted her to grow beyond that into something else — but I didn’t want anyone to see that at first,” Winter says.

When Ellen Lewis, who cast the pilot, suggested Macdonald, he and executive producer Martin Scorsese were instantly sold. “She was, in my mind, the prototype for the role,” Winter says. “Someone who has an innate sweetness and likability to her but also an emotional depth and an ability to be a sort of chameleon.”

Macdonald’s 1996 big-screen acting debut in the cult film “Trainspotting” — in which she played the minx-like schoolgirl who seduces Ewan McGregor’s character — hit the screen like a rush of heroin in an addict’s vein: fresh, electric and leaving the public jonesing for more. Irvine Welsh, who wrote the source novel, was so inspired by Macdonald’s performance he wrote her version of the character into a follow-up novel, “Porno.”

That breakout role, however, almost didn’t happen. Macdonald had been working in a Glasgow pub a year earlier, with fuzzy plans to “maybe go to art school” like a number of her friends. But then a flier advertising open-call auditions for a little film about heroin addiction caught her eye. “Do you want to be the next Sharon Stone?” it read.

“I was waiting for my life to sort of start. I knew I wasn’t there yet…. As soon as I got the part, I knew this was the thing.”

Macdonald went on to work with some of the best directors. Danny Boyle’s “Trainspotting” and Robert Altman’s “Gosford Park” led to the David Yates’ BBC miniseries “State of Play” and his HBO movie “The Girl in the Café.” And then there was the Coen brothers film “No Country for Old Men,” which she sees as a “pivotal” turning point on par with “Boardwalk.”

Even so, the idea of working with Scorsese terrified Macdonald at first. Her only impression of him was from pictures, circa the 1970s. “Kind of serious, the eyebrows and the dark hair — intense. I was quite nervous,” she says. “But … he’s just a lovely human being. He’s like your favorite lecturer at university or something.”

The second season of “Boardwalk” has Margaret Schroeder taking an even more assertive role, she says. In doing so, Macdonald keeps Buscemi on his toes during filming. “She totally becomes another person. Her accent is different, her whole being just seems to really change. I have to be really focused to stay on par with her,” he says.

Despite being married to a rock musician (Dougie Payne, the bassist for Travis) and jet-setting between Glasgow and the Lower East Side of Manhattan (“Boardwalk” films in Brooklyn), Macdonald insists that her life (which includes 3-year-old son Freddie) is relatively normal. She doesn’t read press clippings about herself and says she hasn’t watched any of “Boardwalk” beyond the pilot.

She now has a handful of other film projects in the works that seem likely to nudge her to the forefront of Americans’ pop cultural consciousness. “The Decoy Bride” is a comedy with David Tennant, and she plays Dolly in Joe Wright’s “Anna Karenina” starring Keira Knightley. Until recently, an animated feature was on Macdonald’s wish list; she recently wrapped Pixar’s “Brave” as the voice of lead character Princess Merida.

Television, however, is where Macdonald’s heart seems to be these days. It gives her the chance to develop not only character longevity, she says, but an ongoing relationship with the audience.

“It’s an entirely different thing than a certain kind of film. It’s more intimate,” she says, gently picking at what’s left of her simple breakfast of wheat toast and a boiled egg. “You’re in people’s living rooms. “‘Boardwalk’s’ changed quite a lot for me here in America.”

deborah.vankin@latimes.com