If James McAvoy gave you the look, you would know it. It would pierce your heart like a tiny dart hocked from a hollowed-out piece of wood. Paul Abbott, who wrote the TV show that made McAvoy a star in the U.K. almost five years ago, has been a recipient of the look. Abbott created Shameless, a loosely autobiographical show about a lower-class family in Manchester, England, in which the oldest sister (British actress Ann-Marie Duff, now McAvoy's wife), in charge of raising her siblings, dates a slick criminal played by McAvoy.

At one point during filming, Abbott spoke to the press about the similarities between the premise and his own upbringing. When he offhandedly told this to McAvoy, who grew up in less-than-ideal circumstances himself the child of a divorce raised mostly by his grandparents in the projects outside Glasgow he was met with the look. "It wasn't even a frown," Abbott says. "It was just like his pupils dilated or something.... He made me feel like a whore a little bit."

McAvoy doesn't remember eviscerating Abbott with his eyes, but he fully admits to being critical. "I judge people very quickly" he says. "There was someone I worked with recently who, within five minutes, displayed all the attributes of a fucking dick, and I gave them the benefit of the doubt. Weeks later I was still there, going 'You're so fucking self-obsessed.' I've spent a long time giving people the benefit of the doubt, and I'm tired of it."

Combine that appraisal with a confession that even in his early twenties he never really liked to go out ("All of my friends got so drunk they couldn't even walk, let alone dance, and you just stand there going 'So what am I going to do?'") and a tangent about lookism in pop culture ("I saw a clip of something this girl has on a humongous fat suit and she's singing that 'my milk shake brings all the boys to the yard' song, and I just felt like, 'That's so disrespectful.' I would not want to be a woman in this industry. Horrible."), and a portrait of McAvoy begins to emerge. It looks a little like a prim, white-wigged 18th-century magistrate.

The reality, says Atonement director Joe Wright, is less stiff. "James is someone who's had to fight," Wright says. "He understands emotional and psychological pain. But I think his natural temperament is very light and very comic." He uses the same word that Abbott does to describe McAvoy: dignified.

Wright first saw McAvoy perform in 2001 in London, in a play called Out in the Open. He had just graduated from the Royal Scottish Academy of Music and Drama one lily pad in the series that every actor from the U.K. seems to traverse before he lands on this side of the pond: a hard-knock childhood in a factory town, a few years at arts school, and a couple of stage appearances that lead to a breakout role in a TV show. But certain details bring McAvoy into sharper focus. There are the grandparents, whom he mentions regularly in conversation (his father left the family when he and his younger sister, Joy, were in grade school). There's the time in high school when he played bass in a band, something he wasn't very good at but which served as a meandering tributary into acting. There's Duff, his wife, eight years his senior. But ask for more details about her, his sister, or any other key figures in these vignettes and you'll get another look a defensive one that's much different from the silent-poison-dart one. It's a lot like the one Matt Damon gives Robin Williams when he walks in for his first therapy session in Good Will Hunting.