Brian F. O'Byrne on 'Brotherhood'

Brian F. O'Byrne on 'Brotherhood'

Brian F. O'Byrne is one of the most respected actors in American theater, although he still isn't a household name. In fact, a lot of people who do recognize his name don't know how to pronounce it (it's BREE-an, in the traditional Irish fashion).

That may change, however, thanks to the actor's current riveting work in "Brotherhood," the Peabody Award-winning but still ratings-challenged Showtime drama airing Sundays.

O'Byrne recently joined the series, now in its second season, as Colin Carr, a long-lost Irish cousin of the Caffees, the Providence, R.I., family at the heart of the series. Although Colin is regarded with suspicion by matriarch Rose Caffee (Fionnula Flanagan), he quickly ingratiates himself with her sons, shady crime figure Michael (Jason Isaacs) and ambitious politician Tommy (Jason Clarke).

"Colin is wonderfully positioned on the series, because he is such a nice foil between the two brothers," O'Byrne says by phone from Berlin, where he is co-starring with Clive Owen in a new film by Tom Tykwer ("Run, Lola, Run").

"The positive thing about immigrants coming to America is that, since they don't have a personal history [here[, they can apply themselves 100 percent to whatever they put their minds to, because they are getting a second chance. Colin is quite bright, but he doesn't have any baggage with anyone in Providence, and yet he is protected within this family. I think Colin is one of the few characters on the show who can go between both worlds. There's something charming about the guy. I think maybe he can lighten the mood between both Michael and Tommy."

Although O'Byrne has done a number of TV guest appearances, "Brotherhood" marks his series debut, and he admits it's a bit of an adjustment playing a character whose personality unfolds on a week-to-week basis.

"I've never done this before and, to tell you the truth, I have found it quite liberating," he says. "Obviously, in the theater, every night you carry home that performance and you think, 'How can I make this better tomorrow?' With a show like this, you just go and do the scenes, and then you have to just let it go. You do your part of the jigsaw as best you can, but in the end, it's not up to me.

"It's possible you could open a script one week and discover that your services were no longer required, and that's a very interesting dynamic. It's fun, because it means you just enjoy the ride while you're on it. It's letting loose a little bit."

Although he has won acclaim for his theater work, O'Byrne insists he never really gave any serious thought to acting while he was growing up in Ireland until two friends decided to enroll in drama school at Trinity College.

"Really, out of just not knowing what I would do if my buddies went away to college, I decided to go and audition with them," he says. "It wasn't something that I had dreamt about or even thought about."

Eventually he made his way to New York, where he quickly found work with the Irish Repertory Company. He rarely has stopped working since.

O'Byrne made his Broadway debut in 1993 in the hit comedy "The Sisters Rosensweig," then scored two back-to-back Tony nominations for his work in U.K. playwright Martin McDonagh's "The Beauty Queen of Leenane" and "The Lonesome West." In 2004, he finally won a Tony for his chilling portrayal of a child serial killer in "Frozen," in which he starred with Swoosie Kurtz.

"That was a great part," he says. "There's a moment in the very beginning, before people really know who he is, where the spotlight comes down on him, and he says 'hello' to a kid who isn't there, and you could just feel the temperature in the theater drop. It was wonderful to experience, because it's just collective imagination and good writing. We had created that incredible moment together. You could feel people being repulsed.

"The only difficult thing about it was that I love kids, and I love looking at their faces smiling as they walk toward me. I found myself having to resist doing that in case the parents had seen me in the show, because that would just not be good, walking around grinning at children."

After yet another Broadway triumph (and, yes, another Tony nomination) in the hit play "Doubt," O'Byrne tackled one of the most challenging roles of his career in late 2006 as Alexander Herzen, the principal character in Tom Stoppard's epic stage trilogy, "The Coast of Utopia."

O'Byrne scored his fifth Tony nod for that part, but the most exciting part of that experience for him came on those rare days when the company -- which also included Tony winner Billy Crudup, Ethan Hawke and Martha Plimpton - performed all three plays in a stunning, 12-hour theatrical marathon.

"On marathon days, people would come in and say, 'I'm just going to let this wash all over me. I'm here for the day.' The show became this wave that just passed over them and, oddly enough, that was exactly what the piece needed," O'Byrne recalls.

"I think we were onstage from 11 to 11, so we got to the theater at 10 those mornings. It really was the nearest thing to a rock concert, because people in the audience really went slightly insane. I mean, we'd see people waving their fists in the air and jumping at the end of 12 hours of Tom Stoppard talking about Russian intellectuals. I think they realized that not many people had shared our experience together."