The Studio Theatre has half a production of "The Woolgatherer," which is to say that one of the characters in this odd, but potentially affecting, two-character drama is soundly played.

The other performance, however, is so wildly misconceived that it distorts the considerable virtues of William Mastrosimone's script. What is intended to be the chronicle of two lonely misfits coming together in the night ends up resembling a psychodrama at St. Elizabeths.

There was good reason to applaud the Studio for choosing to give "The Woolgatherer" its Washington premiere. Mastrosimone is one of the rising young talents in the American theater, a playwright whose writing combines incisiveness with lyricism. Although he can build scenes of brute theatrical power, that power never overwhelms the delicacy at the heart of his work. More importantly, he has the rare ability to connect seemingly bizarre and marginal creatures to the rest of the human race.

The self-described "cooped-up wackos" of "The Woolgatherer" are Cliff, a long-distance trucker, whose crude exterior masks a deep ache for companionship, and Rose, the fragile salesgirl who works the candy counter at the five-and-dime. She is one of the walking bruised, not unlike the tormented heroines of Tennessee Williams who are traumatized by the blatant cruelty of the world. But if Cliff displays the oafishness of a Stanley Kowalski, he is also a creature of rough-hewn compassion. Picking Rose up for a one-night stand, he slowly discovers that they are both prisoners of a kind--he, locked away in the cab of his truck; she, caught in a world of deeply etched fears. The meshing of these two sensibilities constitutes the subtle, but rewarding, action of the play.

Not at the Studio, however. While the swarthily handsome Robert Carroll holds up his end of the bargain, giving a sturdy and likable performance as the gruff trucker, Nancy Robinette has chosen to play the salesgirl as the ultimate basket case. Mastrosimone has provided the character with some lovely speeches--including one about the senseless massacre of four cranes at the zoo--but Robinette consistently undercuts the haunting words with her fluttery, fidgety mannerisms. This is the sort of performance that makes Sandy Dennis, hitherto the queen of the quirky gesture, appear a virtual corpse.

As a result, Mastrosimone's dramatic equation is thrown totally out of kilter. It is inconceivable that Cliff would ever pick up this loon, and if he did, remain in a room with her for more than five minutes. The sexual charge that necessarily underlies their encounter is constantly defused by Robinette's insistence on making a face and bolting like a jack rabbit each time she is touched. After a while, even poor Cliff begins to look like what he is not--a good Samaritan of cosmic patience with a charity case on his hands.

Robinette's performance is so excessive that one hesitates to place all the blame on her. Behind the nervous tics, one senses the hand of director Sue Crystal. By encouraging such extravagance, however, Crystal has permitted the actress to go over the edge and take a singularly appealing play with her.

THE WOOLGATHERER. By William Mastrosimone. Directed by Sue Crystal; set, Ken Wilson; lighting, Hugh Lester; costumes, Jane Schloss Phelan. With Nancy Robinette and Robert Carroll. At the Studio Theatre through March 28.