SOME PEOPLE over at Quincy House have pulled a neat stunt this week. They have produced two one-act plays, but somehow ended up with about five-sixths of one one-acter. I guess it shows a certain amount of good old American ingenuity on their part, but it also makes for an unfortunately disturbing evening of theatre.

Of course, there are actually two plays on the Quincy House dining room stage these nights, but each one is there in fragments--half of the first (It's Called the Sugar Plum) and a third of the second (The Indian Wants the Bronx). You might want to check my mathematics, but I think that comes out to five-sixths.

It's rather callous to talk about theatre (or anything, for that matter) in terms of numbers, but in a way this production lends itself to such treatment. Director Christopher Arnold has been pretty callous himself in his handling of these two fine Israel Horovitz plays, and I am still in the mood of the evening he created.

What Arnold has done, and it is a grievous error, is underestimate his playwright by playing only for the surface values. While he does well by Sugar Plum and Indian on the superficial level, I don't think Horovitz would be too pleased with the overall result.

In Sugar Plum, he has written about a meeting between a coed artist and the boy who had run over and killed her finance with his car. The whole thing is ludicrous in a Murray Schisgal sort of way; no sooner does the girl arrive, indignant over the death of the man she loved, than she sets out to make it with the killer.

As the girl, Marcy Schuck is cool and brassy and very funny. Her melodramatic longings for her loved one (she keeps talking about how she misses her fiance's "hands on her breasts") seethe with phony sentimentality. And when she falls in love with her new acquaintance, she does it with a wide-eyed bogus innocence that is just right. (On hearing that the boy has a job carting meat, she stares right at him and says, "I adore meat. I think it's really wonderful that you handle meat. Meat is the essence of life." It's at once credible, absurd, and hilarious.

Yet, while Miss Schuck keeps up her half of Sugar Plum, the other and more important half just isn't there. The boy she meets is at the heart of Horovitz's piece; here is a kid who wants to be sensitive, wants to be a poet, wants to be in love. True, he is awkward and amusing (He writes poetry he does not understand, paraphrased from Zen poets), but he is also a human being. As performed by David Pollock, though, he is a silly comic prop--a cardboard version of Art Carney's Ed Norton characterization.

While much of the blame must go to the performer, I feel most of the responsibility for this vacuum belongs to the director. He evidently has not bothered in the least to get anything more than a shell of a character from his actor. We get waving hands for nervousness; pained looks for sorrow, moody line readings for introspection. With no central character around, we must work too hard to find out what Horovitz is talking about. Finally we give up and watch the proceedings as we would a Sid Caesar sketch. While some of the laughs are there, the play isn't.

LIKEWISE, Indian, the better and more serious piece, runs amuck. Arnold has failed to see that Horovitz was not writing just a sharp TV script about the brutal terrorization of a non-English speaking alien lost in New York. Rather, this play is foremost a work about communication. Joey and Murph, the two violent toughs, are as lost as the Indian. They find themselves in a world where their mothers are whores, love has no relevance to them, and nothing makes any sense. They must step on a helpless creature, if only to prove to themselves that they are alive.

All the inner meat of this play is lost in the performance. Once again, the actors (Pollock and Ward Abronski) are convincing on the surface. They look and, with a few lapses, talk like hoods. But when they are not perpetrating evil, when they are just talking among themselves like two life-sentence criminals waiting it out in jail, the play becomes dull.

Even though the secondary lines of suspense are lost (such as the battle between the hoods for the superior role in their relationship), I must give Arnold credit for playing the main plot line to the hilt.

He is particularly helped by his own performance as the Indian, a role that fortunately does not relate much to the more subtle aspects of the play and therefore can exist in full force within this production.

And it's a hell of a lot of force. Arnold dominates the play from the beginning, even when he has no lines and merely stands by the bus stop, shivering and listening to the strange histrionics around him. When the hoods attack him, the abject terror transmitted through his eyes make him an image of helplessness almost unbearable to watch. The climax--he is left on the sidewalk, a bleeding dog barking the few words of English he can say yet does not understand ("HOW ARE YOU? YOU'RE WELCOME! THANK YOU!")--absolutely tore me apart. If only everything else in this production hadn't tore Horovitz apart, these Quincy House people might have had something great here.