London

"This is really exciting!" said Cillian Murphy, perking up. It was a dreary, drizzly day, and he had spent much of the afternoon trapped in his one-bedroom apartment in north London, playing computer soccer, and waiting for his new washing machine to arrive. But now the front buzzer had sounded.
Mr. Murphy leaned out of the window into the rain (his intercom was broken), calling for the delivery men to come inside. An inaudible shouted exchange followed. "His buddy has pulled a muscle and no third party is supposed to help them, but I'm not waiting anymore," Mr. Murphy, 27, explained in his undulating Irish accent. He charged into the stairwell and promptly locked himself out.
So it goes when you are, possibly, on the cusp of stardom but still live in the same old walk-up, whose main design elements are a tall stack of CDs in the living room and the huge ripped-up sofa that you found on the street. Mr. Murphy, who starred in the hit horror film 28 Days Later... and will appear in two new movies, Girl With a Pearl Earring, which opens on Friday, and Intermission, which is set to open in March, is as yet thoroughly unspoiled, having acquired no entourage, no flunkies and no one, it seems, to water his spider plant, the leaves of which are curling reproachfully behind him.
Whether he is playing a man who wakes to find that most of the population of London has been wiped out by a killer virus, as he did in 28 Days Later...; a sad-sack Dublin shelf-stacker, as he does in Intermission; or a bold young butcher romancing Scarlett Johansson in Girl With a Pearl Earring, Mr. Murphy (whose given name is pronounced KILL-ian) brings a fluent ease to the roles he takes on, a graceful and wholly believable intensity. His delicate good looks have, as much as his acting prowess, caused people to mark him as Ireland's next Colin Farrell, albeit one who seems less likely to be caught tomcatting around or brawling drunkenly at premieres.
As it happens, Mr. Farrell is an old friend of Mr. Murphy's and also appears in the ensemble cast of Intermission, as a Dublin hood with a volcanic temper who is on the run from the police. Mr. Murphy's role is less flamboyant, but pivotal nonetheless—his character's romantic mishaps set off a long roundelay of events that touch on the lives of a wide group of friends, relatives and enemies. Having grown up in Cork, in southern Ireland, Mr. Murphy said that the inarticulately insecure character he plays is wholly recognizable.
"Everyone has access to that loser part of themselves," Mr. Murphy said. "He's representative of a certain type of Irish male, particularly in the way he tries to fix things when they're obviously not broken. Even though things are going really well with his girlfriend, he just starts dwelling on it, and finally she says, 'Look, I can't deal with this,' and goes off and finds another fella."
Surprisingly slight, with stunning, wide-set blue eyes, Mr. Murphy was wearing a pair of dark corduroys and a well-worn sweater with a hole on its sleeve. The son of two schoolteachers, Mr. Murphy was not meant to be an actor. It was unclear, however, what he was meant to be. Music was his passion, and he and his younger brother formed a band called, in an homage to Frank Zappa, the Sons of Mr. Green Genes. Mr. Murphy played the guitar and sang; the performances were heavy on extended guitar and drum solos. "It was very much like 20-year-olds showing off how proficient they are with their instruments," Mr. Murphy said, flashing his deep dimples.
Deciding not to pursue a record deal—"my parents were horrified at the idea of us being lost in the vicious claws of the music industry"—Mr. Murphy spent a year and a half not pursuing a law degree at the local college, either. "I signed up only because it was like 10 hours a week," he said. "But I failed the first year, and I really had no ambition to do it."
He had begun to haunt a local theater that goes by the quaint name of the Corcadorca Theater Company (the name, pronounced KIR-ka-DIR-ka, apparently refers to a section of Cork, or else to "guys you see lying drunk on the street," Mr. Murphy said). "I used to hassle the director to give me an audition," he said, "and finally I got one, because of my persistence in annoying him."
Mr. Murphy was cast in Disco Pigs, a two-character play about a young Cork couple, which was initially supposed to run for three weeks in a 40-seat theater. But it was an unexpected hit, transferring to Dublin, winning awards at various festivals and finally opening for a short spell on the West End.
Since then, the continuation of Mr. Murphy's career has been just as unexpected as its beginning. After 18 months in Disco Pigs, he appeared, not very happily, in an Irish production of Much Ado About Nothing, playing what he describes as "the love interest." As he is discussing the part—which was hard for him, he says, because he had never attempted material like that—he can't recall the name of his character and finally gives up. "He was the most boring character in the whole play," Mr. Murphy said. "I will have to revisit that character and do a better job with it in the future."
In the next few years, Mr. Murphy appeared in, among other projects, Sunburn, an American independent film that played in some festivals; The Trench, a small British film set in a wartime trench in which his character was blown up in the first half-hour; and The Way We Live Now, a lavish British television dramatization of Trollope's novel in which he played an idealistic young man with a nose for business and an inability to decide which sort of woman he prefers: virtuous or not.
As he is discussing his career, Mr. Murphy gets up several times to help the washing machine deliverer secure the new appliance in his kitchen. Venturing into his stairwell, he locks himself out again. He says it is a common occurrence and that when there are no reporters around to open the door, he goes down the street and hangs out at the local pub until his girlfriend, an artist, returns.
"The characters that are a bit darker, a bit more ambiguous, appeal to me," Mr. Murphy said, settling back down in his favorite chair, another item he liberated from a garbage pile on the street. "I like characters that are torn between good and bad," he said. Which is why, though 28 Days Later... was his biggest success so far, it wasn't his favorite role. "It had a fantastic script, but most of it was about running away and screaming and shouting and fighting," he said. "The star of the movie was the premise."
While he has no plans to do anything so drastic as move to Hollywood, Mr. Murphy is reading a lot of scripts, interspersing film roles with acting onstage, and still adjusting to all this new gainful employment. His parents, he said, are delighted at their son's success in his unexpected profession, "as long as I'm busy and engaged in some way and keeping my mind occupied, and not bumming money off them."
At the end of the interview, he checked his washing machine and confirmed that it had been successfully hooked up and switched on. He was, he said, looking forward to using it.