"Scenes From Soweto" is one of the most graphically disturbing plays to hit Washington. It also is one of the most politically powerful. It is a brutal, bitter blast at the South African government, and, by implication, at any kind of totalitarian terror.

There is no long-winded political haranguing going on at the Back Alley Theatre, where the play's run has been extended through Feb. 11. Steve Wilmer based the script on the true story of a personal friend, and his work is free of ideological abstractions. It's also free of fat: lean and swift and barely an hour long.

Wilmer tells the story of a black South African mathematician who tries to remain above his country's battles while at Oxford but is drawn into them, more or less against his will, after he returns home. In the final scene, he is stripped and tortured by South African police. A slide projection tells the audience that the character on whom the play is based died mysteriously while under police custody.

Ray Green has several dazzling moments as the mathematician. His dawning awareness that he is inexorably involved in his country's struggles can be seen flitting across his face like the sense of a terminal illness. He squirms and screams with piereing effect in his final moments.

Carlos Cardona has a more technically difficult role, portraying all the whites in the entire play through several accents and postures. None of Wilmer's white characters is deeply developed, and Cardona appears more comfortable in some of his roles than in others. He is particularly convincing as the well-meaning white South African colleague of the mathematician.

Fredric Lee's direction does not dally, with the result that "Scenes From Soweto" is like a quick thunderclap announcing a furious storm.