In "The Blood Knot," playwright Athol Fugard concentrates the trauma and torment of apartheid into one small room. The Washington Stage Guild opens its second season with an uneven but commendable production of Fugard's powerfully simple play, which brought the South African activist to the attention of the world.

Within the miserable walls of that room live the two illegitimate sons of a black mother: Morris Pieterson, whose father is white; and his half-brother Zachariah, son of a black father. Morrie has improved his lot somewhat by passing himself off as white and working as a guard in Port Elizabeth, barring entrance to nonwhites. But he has returned, guilt-ridden, to his brother's rude hovel in the nonwhite slum outside the city.

Their life together is an airless, joyless one. Zachariah resents his brother's passive tyranny, missing fun, friends and especially women. Morrie reluctantly agrees to arrange a "pen pal" for illiterate Zach, but when his little lies reap a response from a white woman who announces her interest in Zach -- and her intention to visit -- panic ensues. Insisting that Morrie take his place at this impossible meeting, Zachariah spends his savings on a "white" outfit for his brother, initiating a bitter, extreme and terrifyingly revealing bit of racial role-playing.

As Zachariah, Keith Johnson makes a complex performance look simple, sparking the play with his sly wit and vitality. John Healey Jr.'s enervated, neurotic Morrie is more difficult to fathom, and his accent wanders distractingly. "The Blood Knot" is a lengthy, circuitous play, with clear allusions to the tale of Cain and Abel, and while director John MacDonald is sensitive to the drama's nuances, he allows the proceedings to drift. The play is performed in the round, and set designer Matthew Cooper has situated the platform stage within a mean, tar paper shack, enclosing the audience as well within its oppressive walls.

The Blood Knot, by Athol Fugard. Directed by John MacDonald; setting, Matthew Cooper; lighting, Christopher Townsend; costumes, Lynn Steinmetz. With John Healey Jr. and Keith Johnson. At the Washington Stage Guild through Oct. 11.