For rising star Cillian Murphy, all of Hollywood's a stage. 28 Days Later... secured his fame and the new Batman will surely cement it, but celebrity is still the one role he won't play.

This has been a significant day for Cillian Murphy, but not in the career-making way you might expect. There are days that have probably been more important: the one, for instance, several years ago when Murphy was standing in line for a Ryanair flight from London to Dublin only to learn he had scored the lead in 28 Days Later..., the artsy zombie movie that went on to become a sleeper hit. Or the night last August in Edinburgh, when he was summoned to Los Angeles to audition for the new Batman just as he was playing his final performance in a three-and-a half-hour stage production of Chekhov's The Seagull.

But this February day—an unusually sunny one for Dublin, the Irish capital that tends to be animated and lively in inverse proportion to its capacity for blue sky—has marked a first for the slight, slim Murphy, who will turn 28 in May. On his way to the Malaysian restaurant on the south side of the city where we're meeting for lunch, a photographer snapped him "just walking the street." The actor's reaction? "I was like, Noooooo!" says Murphy, prolonging the word in mock agony, though his grievance is clearly real. "It's a horrible thing," he explains of the sort of invasion that, in truth, is likely to become more frequent. "For me, as much as I adore acting, when I'm not doing it, I don't even think about it. I don't live and breathe it." Nor, he makes clear, are the press entitled to live and breathe him.

On the other hand, Ireland, in particular, has always loved a homegrown star, and the country clearly has one in Murphy, who has been a near-constant presence on film and (in the U.K. and Ireland, at least) on the stage, of late. The lazy thinking on the subject has been to lump him with Colin Farrell, Murphy's co-star in the recent movie Intermission, an ensemble effort from theatre director John Crowley in which Murphy plays John, the romantic misfit. (The two actors are friends, even if, concedes Murphy, "I don't see Colin as much as I would like.") But with his pale blue eyes and almost diaphanous skin, Murphy couldn't look less like Farrell, and he cuts a totally different performing figure. While Farrell looks to be cornering the market in rogues—a blokeishness that spills over into reports of his off-screen escapades—Murphy possesses a full-lipped intensity that finds him perfectly at home in a period piece like Girl With a Pearl Earring (in which he plays Pieter the butcher, romancing Scarlett Johansson's bejewelled Griet).

And yet, Murphy can dim the doe-eyed sensitivity. This is an actor, after all, who launched his career in 1997 in the play Disco Pigs and its subsequent film version. In both, he played Darren, a.k.a. "Pig", a teenage psycho from Murphy's home city of Cork who thrives on antisocial behaviour and gets off on starting brawls. The character is as willfully self-destructive as the lovesick, suicidal Konstantin—Murphy's Edinburgh Festival role in The Seagull—is woefully so. Small wonder that, as Murphy notes wryly, he's "always kind of playing 'damaged.'"

For proof, one need look no further than the theatre role that's keeping him occupied well into April. As Christy Mahon, the braggart of the title in J.M. Synge's 1907 play The Playboy of the Western World, Murphy fully captures the roof-raising brio of the County Mayo tearaway who ends up transfixing an entire town with a story of patricide that, of course, turns out to be false. But Murphy goes where many stage Mahons don't, capturing the loneliness and loss that exist beneath Christy's preening. "Synge described it as a comedy, but it's patently not; it switches from tragedy to farce to pathos and just goes like that within a line."

We're speaking over a vegetarian lunch with many hours to go before this evening's opening night performance, and Murphy talks of needing to "save [his] voice"—and then rather endearingly doesn't, warming animatedly to one theme after another in the course of several hours' chat. "I didn't train, ever, and I'm constantly trying to educate myself in theater, and I feel you learn as an actor hugely on stage. You're seeing through the arc of a character right from the beginning, and that can only help you as an actor, rather than acting in moments, as you do on film." Not that Murphy craves help so much as he does that feeling—crucial to any actor—of moving forward: "My objective is to improve, and this is the best way to do it. I consider myself an actor, not a film actor or a theatre actor, just an actor, and whatever medium offers the best challenge at any given time is what I take."

Another way to better your art is to diversify your pool of collaborators, as Murphy has surely done. Last year, he spent a week in Romania hanging with Jude Law and Natalie Portman on the set of Cold Mountain. Murphy's role as a Union soldier was small, but the movie's impact on him was not. "We were freezin', man, but just to be involved in something like that—every director should have Anthony Minghella's ability to instill calmness, which, I'm sure, percolates down to the fucking catering. Here was this gi-normous production, and Anthony was like a little Buddha." As for Girl With a Pearl Earring: "People aren't going to go, 'Hmmm, tell us the history of Pieter the butcher.' He's there; he's a device, and I did it as best I could, despite my unfortunate wig."

If nothing else, the film gave Murphy a first-hand glimpse of the kind of stardom that can beset the really young—leading lady Johansson turned 18 while the movie was being filmed. "Scarlett is a cool girl, and I wish her everything, but I hope she hangs on to that essence of what she has. If that shit had happened to me when I was 18 or 19, I would have turned into a dickhead," says Murphy. "I would be an asshole now." That he isn't honours what he refers to as "a very solid upbringing" as the oldest of four children, and to his relationship of seven years with an Irish artist, Yvonne, who graduated last year from London's Royal College of Art. (The two live in the Queens Park area of northwest London.)

An inbuilt sense of proportion no doubt helps too. "I abhor the idea of a personality or a celebrity; I know everyone says that, but it deeply offends me." To that end, he doesn't have a personal publicist—not yet, anyway—and says that three agents (one each in Dublin, London, and Los Angeles) more than suffice. "I've got a lot of people in my life: I don't need any more, and I don't do a huge amount of publicity, really." (Among other things, he has vetoed all live TV appearances and chat shows.) Murphy grimaces as he recalls showing up at a recent shoot for another magazine; it was a joint shoot with two other young actors, and he was the only one without various hangers-on in tow. "They couldn't get over the fact that I was on my own, and I couldn't get over the fact that these guys had an entourage. It seems to me that's the periphery of acting—that's the least important part. That should be the bit you invest with the least amount of energy so that when you have to do the work, you bring the most amount of energy to that. The most important part is work." Murphy speaks admiringly of actors like Billy Crudup, Phillip Seymour Hoffman, and Johnny Depp as welcome escapees from the PR machine. "They don't need to do it, so I don't fucking need to do it, you know what I mean? And nobody's grooming me or pushing me to do something I don't want to do."

Fair enough, but what happens come to the start of shooting at London's Pinewood Studios in May on Batman: Intimidation in which Murphy plays The Scarecrow to Christian Bale's title role? The fifth movie in an extraordinary franchise will surely obliterate any remaining anonymity. "I think I'll be all right, you know?" As reflective as he is opinionated, Murphy muses on the vagaries of a career that he knows has only just begun. "It's obviously surreal, but that's the beauty of the thing. I love the fact that the job we do can be so random, you known, though ultimately it's all the same. Ultimately it's about being true to the script. Ultimately it's about giving a good performance." With that, Cillian Murphy excuses himself, appearing a few hours later on a small stage in Dublin to try out his latest role.