Even when tempers curdle and the talk turns shrill, a sweet and delicate harmony rises from the four cast members of "10 Unknowns," the searching new play by Jon Robin Baitz that opened last night.

Ah, how satisfying it is, this sense of actors so completely attuned to their characters and to one another. Habitual theatergoers may be nagged throughout the first act by a feeling that something is missing in this production at the Mitzi E. Newhouse Theater at Lincoln Center, something they've been conditioned to expect. The answer is simple: it's the sound of wrong notes going clunk.

To my knowledge, Donald Sutherland, Justin Kirk, Julianna Margulies and Denis O'Hare have never before shared a stage. But in relaying this layered tale of art, commerce and corruption, they exude the authority of a veteran string quartet arriving at its big intricate passages gradually and inevitably. This is as smooth as acting gets without turning slick.

It helps, of course, that Mr. Baitz, author of "The Substance of Fire" and "A Fair Country," is without peer among his contemporaries in creating dialogue that spontaneously conveys a character's social context and moral limitations, not to mention a self-consciousness about both. And the New York art world of the 1990's, as perceived from the disapproving distance of a painter in exile, is a perfect devil's workshop for this sharp-edged wordsmith.

"10 Unknowns," however, does very much need the performance it has been given under Daniel Sullivan's appealingly unobtrusive direction. In the name of poetic justice, Mr. Baitz brusquely pushes his characters into places and postures that don't come altogether naturally.

While the first act is terrific, as adroit a setting up of character and situation as has been seen in recent years, the second goes exasperatingly soft, taking psychological shortcuts and cheating itself of a two-fisted dramatic ending.

Still, the pang of emptiness you may feel at the evening's conclusion comes partly from having to leave such richly articulate company. Whatever its flaws, "10 Unknowns" has a breadth and complexity lacking in, say, "Proof" (also silkily directed by Mr. Sullivan), this season's mainstream cerebral hit on Broadway.

The shape of "10 Unknowns" directly recalls that of "The Substance of Fire" (1991), still Mr. Baitz's most fully realized play. Once again an aging cultural lion roars in judgment to a trio from a younger generation over the money-driven disfiguring of a world he once loved. This latter- day Lear is a painter, Malcolm Raphelson, instead of the bilious publisher played so memorably by Ron Rifkin in "Substance."

Since he is portrayed by Donald Sutherland, Malcolm is a shade mellower than his antecedent. The sly Mr. Sutherland, however, manages to find the menacing imperiousness in being laid back. He's passive resistance covered in barbed wire.

Malcolm, a figurative painter, has been living in a Mexican village for 28 years, a casualty of the vogue for Abstract Expressionism ("10 Unknowns" refers to a long-ago art show in which Malcolm was featured).

Now it is 1992, and into Malcolm's earthy studio — handsomely conjured by Ralph Funicello's sets and Pat Collins's lighting — has descended the utterly urban Trevor Fabricant (Mr. O'Hare), a South African- born art dealer in New York. A weather vane for the winds of taste, Trevor senses a new "longing for authenticity" that could make resurrecting Malcolm a lucrative enterprise.

It helps that with the assistance of Judd Sturgess (Mr. Kirk), a young artist who is Trevor's sometime boyfriend, Malcolm is experiencing a new period of productivity. Enter Julia Bryant (Ms. Margulies), a comely graduate student doing field work on a species of frogs that appears doomed to extinction. (And yes, that's a winceably symbolic career choice.)

Watching these four diverse souls butting ideologies in the first act is a sophisticated treat, a contemporary answer to the smart, probing talk of the plays of the S. N. Behrmans and Robert Sherwoods of decades ago. The newcomer Julia, after listening for a few minutes to the sparring men, wonders open-mouthed, "Is this what conversation is like?" If only it always were.

Eloquence flows as naturally as saliva in the mouths of these four, and it's especially gratifying to hear Trevor's glib spiels keep exploding in midmetaphor. The brand-name references, whether it's to John O'Hara and de Kooning or Burger King and the Whitney Biennial, are as spot-on as Jess Goldstein's sociologically exact costumes.

Nor has Mr. Baitz, while obviously sympathizing with Malcolm's contempt for an age of gilded surfaces, overly loaded the dice. Malcolm may wax livid about a world that is exploiting itself to death, but he is not without his own analogous sins.

To divulge much more would be unfair to "10 Unknowns," which anticipates the revelation that concludes the first act with a skill that you appreciate only after the fact. (Mr. Sullivan's steady hand is much in evidence here.) Suffice it to say that this is the element sure to generate heated arguments in Chelsea and SoHo.

The second act takes off from this revelation in ways that are ultimately unfair to the characters. In a play that makes reference to "Pinocchio," Julia emerges as the Jiminy Cricket figure, a chirping conscience incarnate. And Malcolm rushes to self-judgment in a way hardly consistent with this slow-moving cultural dinosaur.

But if such manipulations make the performers uncomfortable, they never let on. The luminous Ms. Margulies, best known for the television show "E.R.," here becomes the girl everyone falls in love with in college, yet there's a grounding humanness about her, a glimmering insecurity. Mr. O'Hare turns in a superbly detailed performance, evident in the South African accent that broadens in proportion to Trevor's anxiety and in the tremulous switches between bullying threats and abject pleas.

The core of the drama, however, is the Oedipal relationship between Malcolm and Judd, and it has been rendered beautifully. Mr. Sutherland sidesteps the obvious fire-spitting for a tense affability that is far more daunting. He also miraculously conveys onstage the same emotional transparency, achieved through the slightest shifts of expression, for which he is famous in films. (Just watch his face when Julia asks Malcolm to paint her.)

It is Mr. Kirk, of "Love! Valour! Compassion!," who gives the show its cracked, conflicted heart. Judd is a familiar Baitz character: the wry, self-destructive gay youth found in "Mizlansky/Zilinsky" and "A Fair Country." But none have lost their irony-centered bearings as affectingly as this one.

Like the movie "Pollock," Ed Harris's wrenching portrait of Jackson Pollock, "10 Unknowns" features a scene in which a painter gazes in anxiety and awe at a blank canvas. In the film, it's a glimpse of artistic gestation. For Mr. Baitz, however, the moment is as much about moral as aesthetic commitment.

To see Mr. Sutherland standing over that canvas, a shrinking Olympian hunched with self-doubts, is to be struck anew by the fusion of moral complexity and dramatic flair that sets Mr. Baitz apart.

10 UNKNOWNS

By Jon Robin Baitz; directed by Daniel Sullivan; sets by Ralph Funicello; costumes by Jess Goldstein; lighting by Pat Collins; original music by Robert Waldman; sound designer, Janet Kalas; stage manager, Roy Harris; general manager, Steven C. Callahan; production manager, Jeff Hamlin. Presented by Lincoln Center Theater, under the direction of André Bishop and Bernard Gersten. At the Mitzi E. Newhouse Theater, Lincoln Center.

WITH: Denis O'Hare (Trevor Fabricant), Donald Sutherland (Malcolm Raphelson), Justin Kirk (Judd Sturgess) and Julianna Margulies (Julia Bryant).