She is an IRA terrorist, and once caught she is persuaded, or pressured, by an earnest MI5 officer - the almost always intriguing Clive Owen - to become an informant, to turn on her brethren. Enough with all this killing and conflict.
Riseborough took the best-actress prize at both the British Independent Film Awards and the London Evening Standard British Film Awards for her performance in Shadow Dancer. She was directed by James Marsh, the Oscar winner for his documentary, Man On Wire.
"Collette was living in a time where the paranoia is so rife you couldn't speak to anyone," Riseborough says, on the phone from New York recently. Shadow Dancer is set in 1993. "Whole families would be involved in the IRA, but they would not know that the other members of the same family were in the IRA."
Which is one of the reasons Riseborough's Collette is so guarded. It's a hushed and inward portrayal - and it makes this thriller all the more suspenseful. What is she thinking? Who does she trust?
"I felt like the strength would be in her silence," Riseborough explains.
The actress, who lives in Los Angeles and Idaho (her boyfriend, the artist Joe Appel, is American), says that she and Marsh were "apprehensive" about the Shadow Dancer project at first.
"The situation in Northern Ireland for us Brits, and for Ireland, had been such a long, drawn out and depressing one, that it was very difficult to find a new angle, a new way of telling it," she says. "But the thing that drew us to Shadow Dancer was that it was being told from a family perspective. And in a couple of hours, we can really get inside this woman's mind."
She also says that the difference between making a small, independent U.K. film ( Shadow Dancer was budgeted at around $6.5 million) and a mega sci-fi Tom Cruise Hollywood affair ( Oblivion had a reported $120 million budget) is - well, there isn't really a difference.
"It's more similar than you'd know. It's the difference of craziness surrounding 35 people, or craziness surrounding 350," she observes, chuckling. "It's either having too little money and no time, or having too little money and no time. It's the same.. . .
"It doesn't work out that just because you're in a big budget picture that suddenly there's loads of money flying around."
Riseborough, who trained at the Royal Academy of Dramatic Art (same as Owen, though he preceded her by several years), isn't showing signs of slacking off. Welcome to the Punch, the heist thriller with James McAvoy and Mark Strong, came out this March and gets a DVD release in July. In Hidden, yet to have a release date, she and her Disconnect co-star Alexander Skarsgård are a couple with a young daughter ( Emily Alyn Lind), facing a storm of supernatural woes. (She likens the film to Rosemary's Baby and The Shining.)
And she just finished her work with an impressive ensemble - Naomi Watts, Edward Norton, Emma Stone, Zach Galifianakis, Michael Keaton - in Birdman, from director Alejandro González Iñárritu, of Babel and 21 Grams.
"It's about a group of actors putting on an adaptation of a Raymond Carver story called 'What We Talk About When We Talk About Love,' " Riseborough reports. "It's a comedy. A very dark comedy."
Riseborough plans to make her own films in the not-too-distant future, too. She has a production company, Mother Sucker, and four projects in various stages of development. She plans to write, direct and star.
"It's called Mother Sucker because I sucked from my mother, and her mother before that," she says, playfully. "I think it's going to be a fantastic adventure, an interesting experiment. . ..
"And I was almost amazed that nobody thought of the name. I figured that at least some seedy porn site would have thought of it!"
Contact movie critic Steven Rea at 215-854-5629 or firstname.lastname@example.org, or follow on Twitter @Steven_Rea. Read his blog, On Movies Online, at www.inquirer.com/onmovies