``I've always been compared to Katharine Hepburn, and it bugged me,'' actress Kate Mulgrew says.

You can almost see Mulgrew's chin jut out as she says this, and if you follow that line up her cheekbone, it's impossible not to see the facial similarities between her and the legendary film star.

Add to that the aplomb with which Mulgrew dispatches orders as Capt. Kathryn Janeway on TV's ``Star Trek: Voyager,'' and the combination of confidence and sensitivity echoes Hepburn's acting style.

So it was almost inevitable a one-woman show about Hepburn would be written with Mulgrew in mind. ``Tea at Five,'' which refers to Hepburn's father's requirement that tea be served at 5 p.m. no matter what, opens Sept. 8 at the American Repertory Theatre after successful runs at the Hartford Stage (where it originated) and the Cleveland Playhouse, near Mulgrew's home.

``I never really cared for any of Hepburn's films,'' says Mulgrew. ``I was never drawn to them, but when (playwright) Matthew Lombardo sent me the script in the midst of `Voyager' taping, I was struck by how such a relatively young guy could capture her so completely. He's tapped into one of her most defining moments, when she is both extremely vulnerable and very agitated.''

The play opens with an arrogant, 31-year-old Hepburn waiting for her agent to call to let her know if she has been cast as Scarlet O'Hara in ``Gone With the Wind.'' She has retreated to the family estate in the Fenwick neighborhood of Old Saybrook, Conn. (where the 95-year-old Hepburn still lives), after being labeled ``box-office poison'' by Hollywood producers. The way she handles the disappointment, and then gathers her courage to go on, creates the drama of the first act.

In the second act, we return to Fenwick in 1983, when the 76-year-old Hepburn - wearing a cast from a car accident and struggling with a Parkinson's tremor - reminisces about her relationships with Spencer Tracy and her father, and the suicide of her beloved brother, Tom, when she was only 14.

The second act, says Mulgrew, is much easier to play. ``It's an actor's instinct to be reflective. It's much harder to find the young show-off, who was extremely agile and dextrous. She was like a very feral cat, who says, `Watch me move.' ''

Since Hartford, Mulgrew says, Lombardo has rewritten the first act to dig deeper into what drove Hepburn to fame.

The play may take dramatic license (Hepburn's niece, Katharine Houghton, who played her daughter in ``Guess Who's Coming to Dinner?'', criticized the play but praised Mulgrew's performance in a letter to the editor of the Hartford Courant), but ``neither the director (John Tillinger) nor the writer had any intention of making this a love letter,'' Mulgrew says. ``They wanted to reveal this woman as she truly was.''

This is a woman who wrote in her autobiography, ``I'm in the business of being fascinating.'' Despite appearing in more than 70 films and writing an autobiography, Hepburn managed to keep the public at arm's length.

``She can write autobiographies till the cows come home without revealing any more than she wants to,'' Mulgrew says. ``Think about it. That's what accounts for her notoriety: her privacy and ability to maintain it. All during her long affair with Tracy, the press left her alone. They did not want to damage her even though they devastated Ingrid Bergman and others for lesser sins.''

After all Mulgrew's research (she read everything written about Hepburn and watched all of her films twice), when she got into the rehearsal room with Lombardo's script, she says, ``I began to fall in love with her, and when you're falling in love, it's very exciting, and nothing is too daunting.''

In her own career, Mulgrew has never seemed daunted. She started out on the New York stage, then landed a part in ``Ryan's Hope,'' an '80s soap opera staple. When TV producers offered her the role of ``Mrs. Columbo,'' Mulgrew resisted, but ``they made me an offer I couldn't refuse.''

That short-lived series led only to a succession of forgettable films, until she got the call to play the first female captain on the third incarnation of ``Star Trek.''

``OK,'' Mulgrew admits, ``Janeway was daunting. The first day on the set, there were 30 guys in suits watching my every move. But I finally said, ``Who cares? Leave the hair alone, for crying out loud. I have to make this part my own.' ''

Playing Janeway for seven seasons has been gratifying, she says, and this year it has had an unexpected bonus. Mulgrew's husband, Tim Hagan, is running for governor of Ohio, and Mulgrew was able to call in the ``Voyager'' cast and original ``Star Trek'' captain William Shatner for a big fundraiser.

``It has been fun to be on the campaign trail with him,'' she says. ``But I'm ready to get back on stage.''

``Tea at Five,'' a Hartford Stage production presented by the American Repertory Theatre, 64 Brattle St., Cambridge. Sept. 8-22. Tickets: $32-$62. Call 617-547-8300, or go to www.amrep.org.