When I asked Celia Keenan-Bolger to name the biggest surprise so far in her work on The Oldest Boy, she replied, “The audience.” Does she mean she didn’t expect that play’s theatergoers to be so calm, excited, fidgety, engaged, or, the actors’ bane, congenitally unable to silence their cellphones? Not exactly. “I mean that I wasn’t prepared for just how intimate a relationship I would be having with them.”

I asked her to elaborate. “In the past, I have deliberately not looked at audience members in the eye. Doing so takes me out of my character. But in this play I speak directly to them.” She added: “It’s important to see and feel how they are receiving things. It helps me adjust my performance, and better serve the storytelling.”

For Keenan-Bolger, who has been Tony-nominated for The Glass MenageriePeter and the Starcatcher, and The 25th Annual Putnam County Spelling Bee, addressing the audience wasn’t the only career departure. “I’ve never played a mother professionally. In Saved,” – a 2008 off-Broadway musical – “I played a girl who got pregnant, but she wasn’t a mother with children, as I am in The Oldest Boy.” Keenan-Bolger’s character, Mother, is also pregnant in act two of The Oldest Boy, and the actress points out that “usually when a character onstage or in a movie is pregnant she talks about it. Not here. Sarah is so good at steering clear of clichés.”

As for the play’s exploration of Tibetan Buddhism, Keenan-Bolger says, “I had to get up to speed on that topic. I didn’t have a religious upbringing, so there was a lot for me to learn.” She absorbed a great deal in the three-week workshop that the cast, director Rebecca Taichman, and the playwright conducted this past June. “We all read a fair amount then,” Keenan-Bolger said, “thanks in large part to the huge suitcase of books on Buddhism that Sarah brought in.”

Later in the summer, Keenan-Bolger did a three-day retreat on Buddhism in upstate New York. “It was a good, low-key, extremely useful experience.” What she learned there, and in rehearsal, about meditation has proved applicable to her general approach to her profession. “I’m becoming better able to not obsess about what comes next. I’m nowhere near being completely peaceful about the future – like all actors, I think about my next job – but I’m less worried with the outcome than I used to be.” Keenan-Bolger says her newfound tools have had another impact: “I can get a little bored in long-runs. With this play I’ve been able to reframe how I look at the experience of the show. I’m a little better at staying in the day-to-day.”

Keenan-Bolger said she is grateful for many things about The Oldest Boy engagement: the play itself, as well as the collaboration she’s had with director and playwright, and with her fellow actors and colleagues backstage. She made a special point, however, of mentioning the note that Taichman sent backstage to the actors at the end of the preview period. Keenan-Bolger explained: “She said that the act of performing is very much like the ritual and repetition involved in religion. Instead of thinking of all this as monotony, we should think of it as an exploration. The goal is to go a little deeper every time you do it.”

Brendan Lemon is the American theater critic for the Financial Times and the editor of lemonwade.com.