Rehearsing an Arthur Miller play in front of Miller himself may sound like an intimidating experience, but Frances Conroy doesn't see it that way. Conroy -- who stars opposite Patrick Stewart in Miller's new play, The Ride down Mt. Morgan -- says the legendary playwright is actually a very nice guy. "He's just this enveloping, warm, simple, friendly presence," she relates. "He's there suggesting things, and making fun of himself at times. He's amazing."

She ought to know. Mt. Morgan -- which opens on April 9 at the Ambassador Theater -- is Conroy's fourth Arthur Miller piece. Her first was Off-Broadway's The Last Yankee in 1992, which earned her an Obie Award. Later, the actress appeared on Broadway in Broken Glass, and in the film version of The Crucible (Miller wrote the screenplay adaptation.) Since he's so active behind the scenes, Conroy says she's seen a lot of the 84-year-old writer over the past decade: "He likes to come to rehearsals. He respects the director, and at the same time, his eye is very concise as to what is happening in the process of realizing a character in a scene, and the play as a whole. And he gives very good notes to actors. They're really helpful."

When Conroy was first cast as Mt. Morgan's Theo last fall, she could've used some good notes -- and fast. The play was making its world premiere at The Public Theater, and the actress was a last-minute addition. "Blythe Danner had been playing Theo, and she needed to leave because she had to take care of somebody in her family," Conroy explains. "That happened after three weeks of rehearsal. Normally, a play rehearses for four weeks, then goes into tech for a week and the audience comes. So, they were in a bit of a bind."

Because of her previous association with Miller, and because she'd been in several productions at the Public, Conroy was handed a script and offered a chance to read with Stewart. "I met him, and I said, `I'm so sorry that this has happened. If it seems like I might fit into this whole thing, then it's great. If not, then it was wonderful to meet you,'" she recalls with a bemused smile. "I started rehearsal the next day."

Despite the tight schedule, Conroy instantly connected with Theo, a middle-aged, happily married woman who learns that her husband Lyman (Stewart) has had another wife and family for the past nine years. Though bigamy may seem like the stuff that Lifetime movies are made of, Mt. Morgan is sophisticated, and often bitingly funny. "That's been the real trip about the audiences," Conroy says. "They are just roaring throughout a lot of the play." Theo delivers many funny lines herself, even though her world virtually falls apart in the first scene, when she meets wife #2, Leah (Katy Selverstone), at a hospital where Lyman is recovering from a car accident. Theo's scenes alternate between past and present, comic and tragic, fantasy and reality. "The first time around, it was hard," she remembers, "The scenes, as you know, jump in time, jump in emotion in such extremes. You figure that the real time is less than 24 hours in that hospital. But there's so much more than that going on."

The role is a challenge, but Conroy is certainly up for it. She's been acting professionally for decades, and received her first professional training back in high school. "I went to the Neighborhood Playhouse for a year on Saturdays," she recollects. "I would take the train in from Long Island. The classes were wonderful." After attending Dickinson college, Conroy graduated from Julliard's Drama Division and went on to attain the enviable position of Constantly Working Actress. Over the years, she's appeared in films like "Scent of a Woman," "Sleepless in Seattle," "Billy Bathgate" and "Crimes and Misdemeanors"; her Broadway credits include a Drama Desk Award-winning turn in The Secret Rapture, The Little Foxes, Two Shakespearean Actors, as well as The Rehearsal and In the Summer House, both of which earned her Drama Desk nominations. She's also appeared in several plays for the New York Shakespeare Festival, including the 1998 production of The Skin of Our Teeth, in which she co-starred with John Goodman.

Due to Stewart's scheduling conflicts, the Public Theater production of Mt. Morgan ran for only a few weeks. So, Conroy's particularly glad she has another chance at it. "I've never done a play a second time. I really enjoy it," she observes. "You already have the knowledge of the character somewhere inside you. And it comes out in rehearsal. It's like meeting an old friend again, and getting to know more about them."

She's also happy to be working with her old friends Miller, Stewart and director David Esbjornson again: "They are these three, loving, lovely men, who have such positive energy."

This time around, Conroy's on Mt. Morgan for the long haul. The Ambassador production is scheduled to run five months. That's a long time to be riding Theo's emotional roller coaster. But rest assured, Conroy will be able to handle it. "I'll just have to eat a good breakfast," she says with a laugh.