" 'Master Harold' . . . and the boys" is a play of hammerlike strength at the same time it is like a caress on the fevered brow of humanity. There is no ducking the brute theatrical force of its final half-hour. But just as unavoidable is its unblinking compassion for this sad species called man, yearning for grace and harmony in a universe that delivers only collisions.

Rare as its qualities are--and they are rare on today's stage--they are what we have come to expect of Athol Fugard, South Africa's most accomplished dramatist and quite possibly the best dramatist the world has to offer right now. In a touring edition that I found superior to last year's Broadway production, " 'Master Harold' " opened a two-week run at the Warner Theatre last night. It is hard to believe that the season will deliver a more consequential production or a performance to match that of James Earl Jones as Sam, a huge, hulking menial in a sorry tea room in the even sorrier South African town of Port Elizabeth.

Fugard's plays are anchored in the harsh racial realities of his homeland, a country that continues ruthlessly to segregate its people according to the gradations in their skin color. Here, his characters--the two black workers in the tea room and Hally, the white teen-age son of the proprietors--are drawn from the ranks of the ordinary. Fugard is chronicling a rainy afternoon in that tea room back in 1950. In the course of the chatter, the reminiscences, and the easy tomfoolery, racism will rear its ugly head for the first time in the life of the white youth.

Up to that irreversible moment, Hally has been a bright brash school boy, who instinctively looked to the two black servants for fun and warmth and solace when his father was too busy, or too drunk, to bother. By the end of the play, he will have traded in the nickname for Master Harold with all the smug superiority that appellation implies. The play is South African to its marrow and really couldn't take place anywhere else.

And yet, midway through a drama that never once inflates its humble particulars or indulges in lofty pronouncements, you will realize that Fugard is indeed writing about all of us. His play is about the gulfs that suddenly yawn at our feet and the scapegoats we make to exorcise our pain. It is about the punishment we inflict on others, when we are really inflicting it upon ourselves.

Fugard's most effective symbol--effective, because it is so effortless--is the ballroom dancing contest, for which the two black men, Sam and Willie, are rehearsing, when they can take time out from scrubbing the tea room floor or laying out the gaily colored tablecloths. Why, Hally wants to know, do they bother? As the two men describe the upcoming affair, miming with clumsy grace the couples gliding about the floor, dipping and swooping like great birds on the wing, cheering at the beauty and excitement of it all, it is evident that the ballroom competition is their one image of an ideal world.

"To be one of the finalists on that dance floor," explains Sam, "is like being in a dream about a world in which accidents don't happen." In life, people collide. And the collision that shatters the camaraderie in the tea room and constitutes the final portion of Fugard's play is overwhelming. It is triggered by a phone call from the hospital, where the tyrannical father that Hally has always feared and hated has been recuperating. Now he is coming home. The youth is at once abject and terror-stricken. In a sudden transference of rage that is as lethal as a lightning bolt, he turns on the two black men who have been his only real companions growing up.

It is a long scene, filled with fury and humiliation for all concerned. (It also calls for Sam to bare his backside in refutation of a cheap racial slur Hally has just made.) But it plays with true grandeur, as Sam struggles desperately to keep the youth from spitting out the irrevocable insult, making the irreparable break. Jones' rough-hewn generosity at that moment is the stuff of nobility, and it is all the more moving for the homely pain and the manly helplessness he is also projecting.

Charles Michael Wright brings to the play's climax a beak-like ferocity that would render Hally insupportable, if Wright did not also understand the frightening feelings of impotence that motivate the character. Quick and callow, Hally is nonetheless a good kid and he may still pull out of the slough of hatred into which he has tumbled. This adroit performance extends the possibility.

Completing the trio as Willie--not so bright as Sam, but just as good-hearted--Delroy Lindo is a creature of likable bewilderment. But what makes him more than a comic counterpoint to Sam is the application he brings to life. The intricacies of the quick step are as baffling to him as the terrible eruption at the afternoon's end, but he keeps striving to understand them both.

Under the author's discreet direction, all three actors usher us through a seemingly tiny confrontation that ultimately proves to be of cataclysmic dimensions. " 'Master Harold' " is a slow-gathering drama. But once it has gathered, you will be unable to avert your gaze from the stage. The moral wreckage is heart-breaking.

MASTER HAROLD . . . AND THE BOYS. By Athol Fugard. Directed by the author. Set, Jane Clark; costumes, Sheila McLamb; lighting, David Noling. With James Earl Jones, Delroy Lindo, Charles Michael Wright. At the Warner Theatre through April 17.