"Scheherazade" is an exceedingly unpleasant play and author Marisha Chamberlain wants it that way. Writing about a brutal rape and its ghastly aftermath, she has pulled no punches, minced no words and censored absolutely nothing.

Here is as graphic a depiction of sexual assault as you are likely to see on the stage. It is acted with scrupulous, not to say excruciating, realism at the intimate Horizons Theatre. The set -- an English basement apartment in a Midwestern city and the street leading to it -- spills over into the audience. So does the action.

In short, there's no hiding from the horror that Chamberlain is chronicling. If we need further evidence that rape is a scourge in our society and that it traumatizes and debases women in a particularly ignoble way, then "Scheherazade" serves a function. On the other hand, the play doesn't bring a great deal of enlightenment -- either psychological or sociological -- to its subject. Once you have experienced the understandable feelings of revulsion and indignation, I suspect you will have experienced it all.

Scheherazade was, of course, the princess of the Arabian Nights who spun a thousand and one tales to beguile the sultan who had threatened to put her to death. In a program note, Chamberlain tells us that Ann, the besieged heroine of her play, incarnates "the 'Scheherazade impulse': the impulse to meet evil, danger, or disintegration of the spirit with invention." To the degree that Ann is forced to humor her attacker's fantasies and indulge his psychotic demands, I suppose Chamberlain is right.

The sultan in this instance is Joe, a sadistic young man about whom we learn very little, other than that he is deeply disturbed and has a girlfriend somewhere. Ann's survival, however, depends on her deciphering his moods and finding (and playing) the momentary role -- lover, friend, innocent or slut -- that will momentarily defuse his fury.

Still, I'm not sure that "the Scheherazade impulse" isn't just a fancy-schmancy term for the old survival instinct. All pretensions aside, the hour or so that Joe subjects Ann to degradation and abuse registers primarily as a protracted torture session. Suffice it to say that the continuing torments involve a Scrabble game, raw eggs, beer and a turtle named Jesus, which is beheaded in an especially unsavory moment. There may be symbolism here, but few spectators will have the equanimity to ponder it.

That the violence often seems gratuitous is no doubt one of Chamberlain's points. Among the swirl of conflicting emotions Ann will undergo is a primal sense of guilt. Why is this happening to her? There is no answer. The very randomness of events makes them doubly terrifying for her.

Then, in the latter half of the play, Chamberlain pulls a switch. Ann has succeeded in escaping the clutches of her assailant, but is so distraught that she views a sympathetic policeman with murderous rage. It is the policeman who now must play Scheherazade and conjure the ploys and stratagems that will keep Ann alive. The ironic turnabout, however, seems imposed from without; it's a writer's device to bring a lopsided work full circle.

The nice thing, dramatically speaking, about crazed characters is that they elude conventional motivation. Anything goes. (They are crazed, aren't they?) Nonetheless, when Joe expresses his passion for Scrabble, you find yourself thinking it could just as well be Monopoly. Why does he befoul Ann with raw eggs and beer and not Perrier and a bunch of broccoli? After the policeman has rescued her, Ann insists on phoning her mother, even though her mother is dead and the phone has been ripped from the wall. This is not so much wrenching as it is merely bizarre.

Chamberlain toys with the spectator as arbitrarily as Joe does with his victim. As theatergoers, we have a right to more. If shafts of understanding can't be brought to bear on so much sordidness -- and artistic order imposed on life's chaos -- then we, too, are being exploited. Unlike "Extremities," an equally explicit play about rape, "Scheherazade" is little more than Grand Guignol with simulated sex.

Consider it a tribute to the blunt honesty of the performers -- Carole Myers as Ann, Bill Whitaker as Joe, and, to a lesser extent, Chris Wilson as the policeman -- that the production has the visceral impact it does. Director Gillian Drake has pushed her cast to the brink. It is impossible not to sympathize with Myers, who manages to hold on to a core of inner strength while being subjected to the sort of humiliations few people even want to talk about. Where she gets the will to prevail is anybody's guess. But it's there. As for Whitaker, he often seems to be operating on pure instinct. His residual boyishness may not redeem Joe, but it adds a perverse coloration to his savage tyranny.

As actors, they are way out on a limb and Chamberlain's script is too full of holes to serve as a safety net. Yet there they are, baring body and soul and advancing bravely into a nightmare. If the theater gave out Purple Hearts for courage in the line of duty, they'd each merit a cluster.

Scheherazade, by Marisha Chamberlain. Directed by Gillian Drake. Scenery, Rick Young; costumes, Peter J. Zakutansky; lighting, Carol Fishman; fight director, Lory Leshin. With Carole Myers, Bill Whitaker, Chris Wilson, Ida Eustis. At Horizons Theatre through March 6.