Bringing to life the formidable Katharine Hepburn alone onstage is challenge enough. For Kate Mulgrew, performing the one-woman show ''Tea at Five,'' which comes to the American Repertory Theatre next month, is only one of a towering load of responsibilities that would bow less sturdy shoulders.

But like the indomitable film icon she inhabits, Mulgrew meets her duties with pluck and pragmatism. She's campaigning for her husband, Timothy Hagan, the Democratic challenger for governor of Ohio. She just moved from Los Angeles to Cleveland, where ''Tea at Five'' is now running. Then there's keeping up with the collection of children she and Hagan have from previous marriages and their respective large extended families.

Piloting the USS Voyager, as Mulgrew did for seven years as Captain Kathryn Janeway on ''Star Trek: Voyager,'' must have been a breeze by comparison.

But Mulgrew has a way of combining her many worlds. This weekend she was scheduled to bring in the entire cast of ''Star Trek'' to Cleveland (''on their own dime and on their own time'') for a fund-raiser that would appeal to her many loyal Trekkie fans. She was slated to perform ''Tea at Five'' and participate in the various events, including a $300 reception following the Friday show and an auction of her Janeway uniform.

''It's a challenge, particularly emotionally,'' Mulgrew admits by phone from Cleveland. ''But my husband is a good role model for me. He does not take personally events beyond his control; he takes things one day at a time. That's not my nature and I'm learning to discipline myself.''

The two met after her mother, Joan, who knew Hagan, suggested that he call her daughter since both were in Ireland at the same time. That was nine years ago, and they've been married for nearly four.

Despite speaking quietly to protect her voice, she still sounds charged up. Mulgrew, who was raised outside of Dubuque, Iowa, the oldest girl in an Irish-Catholic family of eight children, has something of the indomitable energy that Katharine Hepburn has always expressed.

''I've watched every one of her movies many times; saw ''Philadelphia Story'' 25 times,'' Mulgrew says. ''And read 20 or 30 books - all of the biographies and everything else I could get my hands on; books on Spencer Tracy, John Ford.''

Matthew Lombardo's play (he wrote it for Mulgrew after seeing her on TV as Janeway and thinking how much she resembled Hepburn), is divided into two parts: The first act takes place when Hepburn is 31, just after she's been labeled ''box office poison;'' the second is when she's 76, right after a car accident in which she almost lost a foot.

Throughout the play, Mulgrew talks directly to the audience in Hepburn's voice - cracked, imperious, and mocking - regaling them with stories about her family, her lovers, her friends, and her career. Filled with contradictions, Hepburn blithely sits out a hurricane and is forever unmoored by her beloved brother Tom's suicide. (The title refers to the family's routine of lively discussions over afternoon tea.)

Mulgrew says the character didn't come together chronologically, as she thought she would. ''The older Kate visited me much earlier than the younger Kate,'' she says. ''Why, I can't say, except to say that at 76, given her reflective, self-deprecating nature, she was easier to understand. I slipped right into her.''

The play had its world premiere in the winter at Hartford Stage, in the city where the Hepburns have roots. In that production, the first act Hepburn had a carapace so thick audiences couldn't see the person inside. So director John Tillinger and playwright Lombardo, along with Mulgrew, collaborated on making changes.

''We've tried to make her less abrasive and more vulnerable,'' said Tillinger. ''It was a down period in [the young] Hepburn's life, but it was all sort of shoved in the audience's face a bit. I felt they needed to know the tribulations that an actress of great talent has to face when there's a reversal in fortune.''

Mulgrew agrees with the changes. ''I have always felt that it was necessary to have more windows into her vulnerability; to show the agitation but see the fear beneath it. Yes, she was driven, but why so driven? If the audience can see me going through the deepest level of what formed her, they will be far more moved.''

During the Hartford run, there was more to deal with than a sometimes rocky script. Some of Hepburn's relatives didn't care for the play.

''I didn't listen to family objections,'' Mulgrew says. ''It was hard not to, because it was all around me, but you have to shut that stuff out. I can understand it. The play is not a vanity piece, but neither is it an indictment. If I were going to see a play about my beloved aunt I too would be ready to judge.''

During that run, Mulgrew developed vocal problems and canceled a few performances. ''In Hartford, she hadn't been onstage in eight years and didn't know what the impact would be on her voice,'' says Lombardo. ''It's very challenging; she had to stay in the back of her throat for 45 minutes. And she was campaigning for her husband. She pushed herself too hard.''

But in Cleveland, she's been fine. ''She knows she has to rest,'' says Lombardo. ''She's in good shape.''

A loyal following

Mulgrew knew at 12 that she wanted to be an actress. ''I was reading a poem to the nuns and they cried. `Bingo!' I said, `This is it.''' She left her home outside Dubuque at 17 and studied at New York University and Stella Adler's famed acting conservatory. Fans may know her from her several stints as Mary Ryan Fenelli on ''Ryan's Hope,'' as Mrs. Columbo, or from guest appearances on other TV shows.

But what's put her on the map is her role as Janeway, who as the first female captain of the Voyager had to keep the crew hopeful as they struggled through the far reaches of the uncharted Delta Quadrant in search of a way home.

When Trekkies heard she was performing in ''Tea at Five,'' in Hartford, they came from all over the globe and helped sell the show out early.

''The fans for `Voyager' have been incredible,'' she says. ''I'm grateful to them both for their support of the one-woman show and the campaign. They've really shown their allegiance.''

As she speaks, Hepburn-like turns of phrase creep in, especially when she talks about what it's like to do a one-woman show. ''It feels like a mountain - Mount Everest, to be perfectly specific. It's extremely solitary. One could construe it as rather frightening. But it's also liberating. You could think of it as flying without a net.''

''Tea at Five'' opens Sept. 8, but the house will be dark on Sept. 11. Mulgrew finds the timing of the show so close to that event fortuitous.

''It's interesting living at such a time of international turmoil, in the wake of 9/11, with the markets diving,'' she says. ''Our culture in part wants to just sit and be reminded of the maverick spirit that defines this country. That's probably why the response has been as wonderful as it has been.

''When a country has been as hard hit as this has been, it's encouraging to sit quietly and watch someone who you know was deeply American, a Yankee to her socks. She's a reminder that that's who we were and who we are.''

© Copyright 2002 Globe Newspaper Company.