DURHAM - Last weekend, Jews the world over fasted for a day in an annual rite of atonement. Football fans waved towels, painted their faces and screamed. Every day, people dance and sing to noise you wouldn't call music, eat things you wouldn't call food, implore the gods for drought-quenching rain.

What's normal for you could be fanaticism to your neighbors, and vice versa. Whole cultures, whole nations, whole races, may strike others as incomprehensible -- even certifiably crazy.

That's the theme of Joe Penhall's play "Blue/Orange," which swept the major London theater awards in 2000 and opens Manbites Dog Theater's 21st season in a stark production directed by Natalie Sowell.

Take one poor young black man with a loose grip on his surroundings, an earnest young white clinician trying to work his way into his profession, and his older white mentor, already immovably lodged there. Put them in a London psychiatric hospital. The result is a laying-bare of cultural presumptions; a pitched battle of interests, personal and public; and a gimlet-eyed condemnation of the psychiatric profession.

Christopher (Trevor J. Johnson) picks up an orange and says it's blue. He's not delusional, he says: There's a tree in Africa that grows that unlikely fruit. He probably knows about the tree from his father, an expatriate Ugandan who has a shipment of East African oranges delivered to his door every day.

His father, he says, is Idi Amin.

Is Christopher crazy? What if he is Idi Amin's son? Does that change the diagnosis? His doctors are at odds, and can't agree whether Christopher should be released or kept for further examination. By prolonging his hospital stay, and his separation from home -- a mostly-black London housing project -- are they helping him or hurting him? Maybe, suggests the senior doctor, black psychosis is beyond the ken of white diagnostics; or perhaps all-black culture ultimately seems crazy to whites. After all, the doctors seem crazy to Christopher: They keep changing their minds, using strange words, lying to him, putting thoughts in his head and then contradicting them.

Penhall's aim is to destabilize all his characters' beliefs -- and maybe, by extension, his audience's. As the play unfolds, Christopher wonders if he wouldn't be safer here in the hospital. The young doctor Bruce (Allan Maule) will risk his career if he stands up to the avuncular Robert (John Honeycutt), who blithely prescribes the "path of least resistance" -- releasing Christopher -- and wants to use the patient's case as fodder for his new book, which advances a tendentious and perhaps specious psychiatric theory. Yet his complacency will crumble, too.

The two men fight over Christopher's fate and try to win him to their side. As their clinical courtesy melts in the heat of merciless browbeating and blame and deception -- turned on each other and finally on poor Christopher -- their entire profession squanders its authority and dignity. Are they themselves driving him mad? Are diagnoses nothing more than ethnocentric projections, vague and empty terms for anything we can't understand -- for other ways of seeing, other beliefs, even other races? Will all of them seem crazy in the end?

Early in "Blue/Orange," Christopher is asked where he lives. "In penury," he replies matter-of-factly. Much later, Robert observes how "the system tends to punish without meaning to." He's talking about patients, but he'll soon see that no one is spared, not even him, and the punishment is penury of the psyche.