Long after Rafael Untalan agreed to understudy the lead role in Oregon Shakespeare Festival's excellent new experimental drama Gibraltar (which runs through Oct. 30), the show's director let him in on a little secret. The principal actor's wife was pregnant. "Oh, and by the way," he was told, "she's due on opening night."

Like an expectant father himself, 37-year-old Untalan, a leading Portland actor adjusting to understudy status in his first year at OSF, felt a mixture of joyful anticipation and stark fear.

This year, it's not just Portland's blue-haired theater buffs and high-school drama geeks making the five-hour pilgrimage south to Ashland. At OSF this season, an unusually high number of understudies have taken to the stage to ensure that the show goes on. As the festival ages (this year OSF celebrates its 70th birthday), so does its company of actors. "Most of the actors are in their late 40s or early 50s. So this year has been really hard for the company. People have lost parents left and right," says Untalan, who understudies a whopping six roles while also regularly appearing in the ensembles of Twelfth Night and Richard III (a must-see spectacle of swordplay and crutches that runs through the month).

In theater, one actor's tragic misfortune becomes another's golden opportunity. Take, for example, this season's best story of understudy heroism, a tale sure to become a permanent part of festival lore. During a performance of Christopher Marlowe's The Tragical History of Doctor Faustus, Sarah Rutan took a flying leap and landed wrong, severely bruising her knee. The stage manager immediately called Rutan's understudy and, legend has it, exactly seven minutes later Georgina McKee made her entrance on cue and in costume. "The understudy nailed it," Untalan says. "She'll be coming back next season. How well you do as an understudy can really assist your career here."

The chance to fill in for the actor one understudies becomes especially important at OSF, where directors select (or reject) actors based solely on how well they performed during the previous year. Untalan is eager to move up through the OSF ranks from stagehand (in Richard III, Untalan functions as a glorified chair mover) to star. "As an actor in Portland, I've been playing lead roles for years," says Untalan, who most recently appeared in Miracle Theatre's 2004 runaway hit Lorca in a Green Dress. "Coming here was a difficult adjustment."

Life as a lead actor's shadow can be lonely. Next time you're in an OSF theater, look behind you: Every house has its own small, glass cubicle next to the stage manager's booth designed especially for understudies. Untalan says he's usually there by himself, propped up on pillows trying to get a good angle, and scribbling notes by a comically dim light. "Watching another actor's choice-making, his relative strengths, his instincts and how he focuses those instincts vis-à-vis the character is a dream," he says. "It's like being a spy in the house of art."

Much of Untalan's work takes place in isolation. As the understudy for a role in the two-person drama By the Waters of Babylon (which closed in June), Untalan wasn't even allowed into rehearsals until two weeks before opening night. "It was a very intimate play," he says. "The actors wanted space to create the work, and I had to give it to them." Still, learning a part with more lines than King Lear without the benefit of blocking frustrated him. "It becomes a different kind of work," he says. "It involves a great deal of imagination. And then when you do get a chance to see rehearsals, you have to honor the other actor's work. That's what you're paid to do. You don't mimic, but you do follow their arc." Because lead actor Armando Durán's father was ill, the director promised Untalan he would take the stage at least once during the run. But on closing night Untalan was still waiting in the wings; misfortune never called Durán away.

Then, one day in June, Untalan got the call. Gibraltar actor René Millán's baby was poised to make its debut. Untalan would have to go on in Millán's place. There was only one hitch: The show hadn't opened yet. "The baby decided to come a week early," Untalan sighs. As a result, he performed only during the technical rehearsal. "That's the downside of understudying, particularly when it's for a meaty role. If you never perform in front of an audience, the process is absolutely incomplete. It's like you have this baby inside you; sometimes it's born, and sometimes it isn't."

Next year, Untalan will return to OSF with regular meaty roles in A Winter's Tale and Cyrano de Bergerac. But this season's not over yet; an entire month remains that could be filled with the unexpected. Here's wishing all the actors: Break a leg.