Actress Sarah Wayne Callies' extensive background in theater trained her effectively for her ascending career in film and television. But at one point it almost doomed her—until a casting director offered invaluable advice. Perform in the room, the director advised. You don't need to reach the 700th person in the second balcony. Disappear for three months and learn to audition for a smaller venue, or you will never get a part.

Living in New York at the time, Callies practiced her material on the subway every day. If people stared at her, she realized she was “;being too big.”;

The result of all the hard work? The 2003 USA network series “;Tarzan,”; her first significant role, and a path to a new career.

Though her character on “;Prison Break”; appeared to meet her demise with a beheading last season, fan outcry at Dr. Sara Tancredi's departure prompted Fox executives to renegotiate Callies' contract for the fourth season—now under way—culminating in a more substantial role than ever.

The Punahou School, Dartmouth College and National Theatre Conservatory graduate plays Tancredi with a subtlety that arose from her own contributions to the evolution of the character.

“;The writers make themselves very available to a dialogue with us,”; Callies said by phone from Los Angeles. “;They make it a real collaboration, which is such a gift because it's not that way on every set.”;

During early collaborative efforts, Callies “;tried very hard to fight for restraint and nuance, because on a show where the action is filled with so many broad strokes (beheadings, for example) ... I felt very strongly that I really had to ground that in a character who was beat-to-beat, moment-to-moment, word-to-word very believable. And very understated.”;

When the script called for Sara Tancredi and Michael Scofield (Wentworth Miller) to kiss, both actors objected. Too soon, they insisted. “;We pushed that kiss back for a long, long time,”; she laughed. “;I think that allowed us to build the tension between them in a way that made it more interesting to watch than a contemporary sensibility when two people are attracted to each other, and the very next scene they're waking up together.”;

With Callies now elevated to a key player on the show, Michael and Sara finally have the opportunity to spend more time together, advancing their relationship. Yet the path is sure to be fraught with wrong turns, since both possess different ideas of what it means to love someone.

“;For Sarah, loving Michael (who has a brain tumor) means caring for him in a way that tries to get him to care for himself and his own health,”; noted Callies. “;Part of that is selfish, because he's the last thing left in her life. The altruistic sense of that is she's the only voice in his life who isn't trying to get something from him.”;

He, on the other hand, doesn't want to think about his health until he's made her safe. The result? Relationship frustration. And there's no end point in sight.

But that's a good thing for Callies. Indeed, new opportunities abound. She completed a feature film entitled “;Hellion”; (also known as “;Whisper”;) with “;Lost”; star Josh Holloway (”;I'm wildly jealous that he gets to work in Hawaii!”; she laughed), and another movie is in the works. In addition, she's shopping a script she wrote. And she manages all of this around parenting her toddler, Keala. Then, of course, there's the constant lure of the stage.

“;For a long time all I wanted to do was to get back to theater as quickly as possible,”; she said of the medium that initially drew her to acting. “;But at this point what matters to me more is to tell stories that people respond to and stretch our sense of what it means to be human.”; Writing allows her to get more involved earlier in the process.

Of her recognition quotient, Callies remains philosophical: “;I think a certain amount of fame in the culture that we live in right now is helpful professionally because it makes you less of a risk to hire. I'm not going to pretend it's something that I don't need. But anything beyond what I need, I don't want. I've seen people's lives up close before and after, and the level of invasion is appalling.”;

Coming of age in the islands, however, has helped her remain grounded amid her burgeoning fame.

“;For the most part, Hawaii's a really modest, practical place, and I'm so grateful to have grown up that way. One of the beautiful things about Hawaii is ... you don't grow up thinking there's one way to be, or one way you should look, or there's one thing that defines success. ... It felt much more fluid and diverse ... which helped me expand my own sense of identity. I also think it made me a better person.”;