HOPSCOTCH by Israel Horovitz; directed by Shaun Miskell; with Laurel Allen and Robert Shampain; and BIRDBATH, by Leonard Melfi; directed by Akim Nowak; with Brian Hemmingsen and Maureen McGinnis. Both plays produced by the Spheres Theatre Company.

At d.c. space, Seventh and E Streets NW, Tuesdays through Sundays until October 12.

The idea that exciting theater can happen in unluxurious, even primitive surroundings is one of those truisms people utter without a great deal of conviction. It takes something like the pair of one-act plays that opened Tuesday night at d.c. space to remind us that truisms can be sometimes true.

It also takes an actress like Laurel Allen, who plays the tough, desperate, saucy heroine of "Hopscotch," Israel Horovitz's two-character play set in a park in Wakefield, Mass. (the author's hometown). Allen can say "I loathe you" as if it were "I love you" -- and vice versa. Dressed in railroad stoker's overalls with a big "smile" button across the front, she displays a riveting emotional fluidity and, while she is at it, all the natural attributes and technical skills of a first-rate actress.

Horovitz has provided her with plenty of opportunity to show her stuff. His play -- about a tense rendezvous between a hometown girl with loose morals and a mysterious visitor from Boston -- has some of the same acidly melodramatic quality as Edward Albee's "Zoo Story." And it has some of the same feel of an archaeological dig in which the hidden stuff of two lives is being brought gradually to the surface.

The wit is bitter and constant. "Anybody ever tell you you got a mouth like a toilet?" asks Robert Shampain, as Earl, the visitor.

"Oh yeah," replies Allen. "A couple of guys. They didn't get very far with me, though. Not with an obvious line like that. You know, maybe a quick feel."

Like Allen, "Hopscotch" is adept at changing moods. Whenever we think we know where we stand, the play finds a way to catch us off guard. And Shampain, while not up to his costar's standard, is comfortable and convincing as the visitor, down to his authentic Massachusetts-ese.

The double bill is aptly described as "an evening of encounters." "Birdbath," by Leonard Melfi, is another two-character play about a man and a woman, in this case a hard-drinking poet who moonlights as a restaurant cashier, and the nervous waitress he invites home at closing time one night. Their improbable alliance and the melodramatic denouement are familiar theatrical stuff nowadays, but the two players, Brian Hemmingsen and Maureen McGinnis, make "Birdbath" involving even when the story and the dialogue are at their least inspired.

Both plays are performed in an upstairs loft that bears only the most fleeting resemblance to a theater. But the Spheres Theatre Company has dredged up a rich assortment of scenic flotsam and jetsam and generally demonstrated that splendid things can indeed be done on a small budget.