By Jeff Labrecque
Updated January 27, 2012 at 08:35 AM EST

Casting Clive Owen as an MI5 operative in your movie is never a bad idea, but in Shadow Dancer, the taut British thriller about espionage and betrayal set during a spike of Irish/English violence in the early 1990s, Owen isn’t some gun-toting super-agent quick with a quip. Instead, he’s a middle-level field officer assigned with recruiting a captured Irish nationalist (W.E.’s Andrea Riseborough) — whose subway bomb failed to explode — to betray her family. “I think it’s a great performance by Clive,” says director James Marsh, a Sundance fave after his heralded 2008 documentary, Man on Wire. “It’s something he doesn’t do enough of, in my view. It’s very understated and discreet what he’s doing in the film.”

In Shadow Dancer, which premiered at the Sundance Film Festival Tuesday night, Owen’s Mac and Riseborough’s Colette find themselves wary partners as the political ground shifts beneath them. “I love the dilemmas of the main characters,” says Owen. “He’s somebody who spends a long time reeling her in, and then develops a conscience when he realizes that his superiors are willing to sacrifice her. I thought it was a great conflict for a character.”

Colette’s predicament is precarious. A devoted partisan since her brother was killed in the internecine crossfire as a child, she reluctantly agrees to inform on her own family, a nest of suspected terrorists/freedom-fighters, in exchange for her release and the continued welfare of her own child. But betraying her blood doesn’t come easy. “You never turn against those closest to you,” Riseborough said after Tuesday night’s premiere. “Even if Clive Owen comes on the scene, you’d still stay loyal.”

Loyalty is the essence of the film, a fact that transcended the political setting and the long depressing history of the Irish Troubles in Marsh’s mind. “It wasn’t a particular personal interest in that historical situation that attracted me,” says the director. “It’s about this terrible predicament that this woman is put in with that impossible bargain she is offered. That was my entry point. You don’t need to know too much about the Troubles, but I think everyone can understand what a traitor is to their own family. And that was kind of how I approached it — as a human drama, as a family drama.”

If Owen’s performance is understated, Riseborough’s portrayal is even more remarkable for its own studied stillness. The actress has the complex contradictory tasks of pretending to behave normally around her increasingly suspicious family, while at the same time conveying to the movie audience her constant fear that her kin can see right through her. “The situation she finds herself in is one of total paranoia, heavy guilt about betraying the people closest to her, and really being trapped by the one thing she’s trying to protect, her family,” says Riseborough. “It makes her inner life very tumultuous and almost paralyzes her into a state of seeming placidity in order to weather the storm.”

It’s Marsh, who humbly claims to be clumsy with actors, who understood what the role required and why Riseborough was the perfect choice. “Her face is such a beautiful instrument for feeling, the way an old-fashion silent film actress would be,” says the director. “She could express so much of the emotional complexity and it’s only done on her face. She’s an extraordinarily good actress.”

The film was well received by the Sundance premiere audience, despite — or because of — a viewing experience described as a “constant state of anxiety,” a comment Riseborough immediately tried to take back for fear of alienating potential moviegoers who perhaps might prefer a more conventional Clive Owen action-hero movie. Viewers like British prime minister David Cameron, who recently made headlines when he strongly suggested the subsidized British film industry funnel more of its resources towards bigger-budget mainstream films. “We’re all trying to [make commercial films],” argues Marsh, whose film is co-produced by BBC Films. “And if you gave someone the script of Slumdog Millionaire, they’re not going to say, ‘That’s a great commercial project.’ So it’s all very well for him to say that, but there’s no formula. If there were, then we’d be doing it. But also, there’s got to be some place for self-expression and for experimentation. If we’re talking about national cinema, I think there is a responsibility to nurture more artistic filmmaking. And that’s really when British film has been most successful.”

Read more:

EW Review: ‘Shadow Dancer’ and more

Sundance Star Portraits: Day 6