A ponderous stage allegory; Abercrombie Apocalypse ''An American tragedy,'' by Paul Carter Harrison. Directed by Clinton Turner Davis.

As the stage lights go up, a liveried black manservant is fastidiously dusting the bric-a-brac and antique furniture of a spotless parlor in the Abercrombie mansion. While he dusts, Culpepper (Graham Brown) pretends to conduct some delicate Boccherini on the hi-fi. A phone call establishes that Culpepper not only manages the Abercrombie estate but also conducts its financial affairs with decisive authority.

Culpepper is momentarily distracted by a radio bulletin reporting the kidnapping of a child from a neighboring estate. His composure and aplomb are more rudely ruffled by the arrival of Jude (Timothy B. Lynch), a foul-mouthed, leather-clad, hair-dyed delinquent, and Bethesda (Barbara Montgomery), his handsome, no-nonsense black companion.

Jude is revealed to be the dropout Abercrombie scion. Bethesda is the practical nurse who saved his life. They have apparently stopped by so that Jude can let Bethesda glimpse the luxury from which he fled to become a drug-addicted rebel with very little cause.

Playwright Paul Carter Harrison alternates between the real and surreal to create the allegory, which he subtitles ''An American tragedy.'' Like the drains of the Abercrombie mansion, the plot is clogged. Its symbols range from the hi-fi music (classics to rock) and the portrait of a gun-toting Abercrombie pere over the mantel to the antique ''Mansion of Happiness'' game in which the characters compete.

Culpepper's character comes across as a kind of latter-day, astutely autocratic Uncle Tom, whose apparent pride in the role he plays and the dead master he serves is finally exposed for its inner weakness. He is the perennial custodian, not yet liberated. Although reviling the macho manufacturer-father whose toxic chemicals killed his black workers, Jude (the prodigal returning after seven years) is no more than a self-pitying overgrown child. Bethesda, the maternally compassionate practical nurse, cradles the mixed-up misfit as previous generations of black surrogate mothers cradled the white children entrusted to their care.

''Abercrombie Apocalypse'' offers numerous revelations without much enlightenment on the complex conflict between good and evil in the context of American race relations. The actors directed by Clinton Turner Davis in the performance at the Westside Arts Theater grapple intelligently with the heavily portentous text. But because of its rhetoric and very portentousness, there are times when the dialogue seems declamatory rather than conversational. Perhaps this was the intent.

The production is meticulously designed, but the play is heavy going.