Stepping out of the box

PROVIDENCE -- William Petersen has played the low-key, precise forensic investigator Gil Grissom on "CSI: Crime Scene Investigation" since 2000. He likes his character, calling him "so flawed, but damned brilliant." But with the show's long and exhausting schedule, Petersen wasn't able to perform onstage. The highly regarded Chicago stage actor was getting itchy.

So when Curt Columbus , the new artistic director at Trinity Repertory Company , called to offer him the role of an Irish undertaker's dissolute assistant in Conor McPherson's "Dublin Carol," Petersen leapt at the opportunity.

"The TV show, it's not factory work . . . but you're making the same thing week after week," he said before a recent rehearsal at the Providence theater. "So to be able to have some different kinds of feelings and thoughts. . . . I spend more time playing Grissom than playing me. Over the course of time, that's hard."

Petersen says he feared that if he went any longer without doing theater, he might get stage fright or lose his skills.

The conditions seemed ideal: Columbus and he have known each other for 20 years and have worked together at various Chicago theaters. So have he and director Amy Morton . But this wouldn't be working again in Chicago, where all his friends are, with the resulting distractions. His first show in eight years would be done in what he gratefully calls a "womb-like situation." "Dublin Carol" begins previews Thursday.

CBS allowed Petersen to leave the show, and his absence was worked into the story line: Grissom, citing personal difficulties, was going to take a sabbatical.

"It's great that they'd let me do it, that a lead actor would be allowed to leave in the middle of the season to do other work," he says. "I think they know how much the theater means to me. If you can't revive yourself and take some risks, then you get too stale."

A CBS spokeswoman declined to comment on Petersen's leave of absence from the show, but Carol Mendelsohn, executive producer of "CSI," said in a statement e-mailed to the Globe, "Billy Petersen brings his immeasurable talent to 'CSI' weekly. He has infused Grissom with nuanced life and made him the smartest, coolest nerd on TV. And like Grissom, Petersen is the leader of our team."

He's equally highly regarded in the theater world.

"Billy is one of the most physically fearless actors around," says Robert Falls, artistic director of Goodman Theatre, who has often worked with Petersen in Chicago . "But there's a real delicacy, sensitivity, and beauty in his work. . . . Even in stillness, you can't take your eyes off Billy. There's an explosiveness under the surface."

Now the actor is sitting at a table in a rehearsal, inhabiting his role as John Plunkett , who's being brought face to face with his sorry life on Christmas Eve. There's not a scalpel or microscope -- Grissom's tools of the trade -- in sight, although Plunkett, too, is dealing with dead bodies. What his life is about is downing glasses of Scotch at the funeral parlor where a mortician has taken him under his wing.

In the course of the play, Plunkett has conversations with a young helper (Daniel Mefford ) and with a woman (Rachael Warren ) who comes with bad personal news. Through these conversations, he tries to sort out his history of alcoholism, betrayal, and disappointment, and perhaps even make some changes in his life.

Petersen leans forward at the table and engages with Mefford, who's slouched in a chair. It's two weeks before the first preview and the actors are occasionally a little shaky on their lines, but there's a strong connection between them.

While Plunkett will make his journey toward self-understanding in Trinity's intimate downstairs space, the Dowling Theater, an actor playing Scrooge will do the same in Dickens's "A Christmas Carol" upstairs on the main stage.

"Both men are damaged to one degree or another," Petersen says. "They're lonely. The holidays can be a treacherous time for people if you don't have the pieces in place for a happy Christmas."

And while Scrooge's journey ends with redemption and a family embrace, there's no such tidy end for Plunkett. "I'm not so sure redemption is it," he says, holding his eyeglasses and thinking. "Hope is more it."

His voice seems to have a hint of his native Minnesota, but he says it's the Irish dialect bleeding through. Spending long days rehearsing can have that effect on an actor.

Storytelling, something McPherson's plays are known for, is an instinct Petersen can relate to; he comes from a long line of storytellers. His mother, the oldest of 12, was raised in the north woods of Minnesota with 10 brothers. "It was all the brothers competing with one another," Petersen says. "Who had the biggest fight, who killed the biggest bear."

And his mother? "If you started talking to my mother, you were there all day."

Their family lived in Chicago, and she took him to a vast array of theater there.

And that's where Petersen got his acting start. He and Morton formed the experimental Remains Theatre in 1979, performing Sam Shepard plays that "other theaters wouldn't touch," he says, as well as works by Spalding Gray and Richard Foreman .

Other Chicago theaters, such as the Goodman, Steppenwolf, and Victory Garden, started inviting Remains to bring works to their stages, and they cast Petersen in their shows. He performed Tennessee Williams's plays, such as "The Night of the Iguana " -- which originated at the Goodman and in which he made his Broadway debut -- and David Mamet's plays, too.

"Tennessee, I think, he's certainly my favorite American playwright," Petersen says. "And David is my favorite modern American playwright."

In 1984, he was performing "A Streetcar Named Desire" in Stratford, Ontario, when film director William Friedkin offered him a leading role in "To Live and Die in L.A. " Petersen, who didn't have an agent, called John Malkovich , another Chicago actor, and asked him what he'd made for his last film so he could negotiate a better salary. But he also told Friedkin he couldn't start shooting until his commitment with Stratford was over. "He waited for me," Petersen says, still in awe. Films just didn't wait for unknown actors. "You can't dream up a career like mine," he adds. "I've been blessed."

Petersen has gone on to do numerous films, but he only bought a house in Los Angeles when "CSI" got rolling. He still considers Chicago his home base.

Columbus, who has surrounded himself with Chicago talent in this show, says he's more than satisfied with his choices.

"I recently watched an hour and a half of rehearsal, and the McPherson text is so beautiful and simple, you need a great actor to speak it simply and beautifully. I knew it was going to be good, I didn't know it was going to be this good."