In his play, "P.S. your Cat Is Dead," based on his novel of the same name, James Kirkwood comes to grips with one of the most pervasive and significant relationships of our time: The householder-burglar encounter.

Kirkwood is a big gun on Broadway he won the Pulitizer for "A Chorus Line" -- but this show is playing (Thursdays through Sundays until Sept. 2) at the Back Alley, way out on 14th Street, where an audience of 100 would be overcrowded. One reason might be the play's kinky sexual overtones, which include sado-masochism and homosexuality, but these are hardly new motifs on the American stage.

The show is intimate, contemporary, unpretentious and above all, a play which can be done justice on a low budget. The seven members of its Washington cast get to the heart of its content -- wild, offbeat humor and the kind of pop psychology familiar from "A Chorus Line" -- very effectively.

The central incident is an encounter between two losers, when burglar Vito Antonucci breaks into the Manhattan loft apartment of Jimmy Zoole, whose small, grubby world has just fallen apart. Zoole is a marginal acotr in television commercials and plays that are going nowhere. He is the author of an unfinished novel which Vito stole in an earlier burglary and then threw away. It is New Year's Eve. Jimmy has just lost his job, his lover Kate has left him in a highly destructive scene, his building is scheduled for demolition and his cat has just died. When he captures Vito and ties him up, the scene is set for an orgy of sadism.

What happens instead is a confrontation in which two objects are transformed slowly into persons. They circle one another warily for a while and finally decide to join forces for a renewed assault on the world that has made them victims. Five other actors serve as background and add to the comic relief, but they remain objects of a sort, stuck in role-playing while the two central characters take the first tentative steps toward an awakening.

Vincent Wayne Anderson, in the role of Vito, has the toughest acting job, requiring mercurial changes of style and attitude, a lot of pantomine and a fie blend of comedy and pathos. In addition, he has to do most of it lying prone, tied up, with his trousers off. He manages it in fine style, and Neil Fuller is almost equally impressive in the less demanding role of Jimmy.

The other roles, if one-dimensional, are well-handled, particularly in the case of Nancy Lepp, who makes a brief, fiery appearance as Kate.