A black SUV pulls up to a tiny, beige house in far Southeast. A woman in dark clothing gets out and enters the house. I count to 10, then follow. 

"This is my friend's house," she tells me when she opens the door. "She's letting us use it."

This may be the oddest rehearsal for a Portland Center Stage production that we've seen.

In Anonymous Theatre, nobody—not even the actors—knows the show's cast list until opening night. Actors rehearse one-on-one with the director in undisclosed locations, and they are allowed to tell only one trustworthy buddy about their involvement, so they have someone to run lines with. On the night of the show, the performers arrive through the main theater entrance and sit among the audience. When it's time for their entrance, they stand and deliver their first lines from their seats. 

"It's every actor's nightmare," says Anonymous Theatre veteran Todd Van Voris (Grimm, The Librarians). "It's like jumping out of an airplane." But performers are thrill-seekers, he says. "We're gluttons for that kind of challenge."

Anonymous Theatre was born 13 years ago at Brown University when four seniors, including PCS regular Darius Pierce, wanted to blur the lines between the audience and the performance. "We had many experiments," says Pierce, "but this one was really successful."

Seattle, Philadelphia and even Sydney, Australia, have staged Anonymous, and there's been a performance every year in Portland since Pierce and his college friends moved here in 2003. Tom Stoppard's Agatha Christie-like murder mystery The Real Inspector Hound and a pre-show about a mom and kid trying to kill each other are on the playbill this year. Otherwise, it's pretty blank. 

At the rehearsal, Pierce and the anonymous actress run lines while his 3-year-old son wanders around the living room with a fat, gray cat. The atmosphere will not be so mellow on opening night.

"Ten minutes before is going to be petrifying," says the actress. "My stomach gets clammy just thinking about it." But the stress fades fast, according to Anonymous veterans. 

"The support that you feel from the audience is palpable," says Van Voris. "It's like going to a tent revival."

SEE IT: The Real Inspector Hound and On the Porch One Crisp Spring Morning are at Portland Center Stage’s Gerding Theater at the Armory, 128 NW 11th Ave., on Monday, Aug. 10. 7 pm. $25.