A giant mask of Harriet Tubman dominates the stage. In the background, shadows move across the set. Gospel singing fills the auditorium. A furtive but hopeful mood is clearly set in the first act of "Sanctuary: The Spirit of Harriet Tubman," which will be performed by the Underground Railway Theater this Saturday at the Gunston Arts Center.

"We call it an epic spectacle in the sense of Brechtian theater and also in its scope of time and distance," says artistic director Wes Sanders. The first act, set in the 1850s, is an account of Tubman's Underground Railway. The second act is about a contemporary Guatemalan refugee who finally finds sanctuary in a black church. Cowritten by Sanders and poet Kate Rushin, the play compares American slavery to today's plight of the Central American refugees.

"The first half of the play you can almost call a study in chiaroscuro, light and shadow," Sanders says. "Because of the movement by night in the whole Harriet Tubman story, it is appropriate to tell that story literally by shadows.

"The second half ... in part ... is about the threatened folk traditions and colorful pageantry of Guatemala as related by the refugee. What happens now in Guatemala happens by the glaring light of day."

Sponsored by El Rescate-Nova, a Central American refugee assistance center in Arlington, and the Hispanic Cultural Society, "Sanctuary" will be performed one night only at the Gunston Arts Center at 2700 Lang St. in Arlington. The performance begins at 7; to get tickets call 528-0522.