Theatre: First night review - Prayers of Sherkin Old Vic, London

His fellow dramatists may wonder which to envy him more: Sebastian Barry's writing talent or the handily colourful collection of ancestors who are the spur to his invention. The Steward of Christendom, the 1995 memory play that put Barry on the world theatre map, affectingly explored the emotional cost of the divided loyalties and contradictions lived out by his great-grandfather, Thomas Dunne, the last Catholic head of the Dublin Metropolitan Police before Irish Independence.

It's one of Barry's great-grandmothers, Fanny Hawke, whose story - effectively suppressed within his family - he tries to reclaim in Prayers of Sherkin, an earlier work that now receives its English premiere in John Dove's beautifully acted, if somewhat boxed-in and stiffly staged, production at the Old Vic. Set in the 1890s on storm-tossed Sherkin Island, off the West Cork coast, the play focuses on the one remaining family in a visionary Protestant sect that had been led to the spot from benighted Manchester, three generations back, by one Matt Purdey in order to await the new Jerusalem.

Marrying out is forbidden, on pain of irreversible banishment, but with the community reduced to the candle-manufacturing head of the household, John Hawke (a powerful Julian Glover), two spinster aunts, a son who isn't quite right in the head (Bohdan Poraj), and a 30-year-old but younger- seeming daughter, the only alternatives appear to be incest or extinction. Is Catherine Cusack's touchingly awkward Fanny to wait for the man whom she is assured the spirit of Matt Purdey will send to her from Manchester, or is she to follow the promptings of her heart and leave with the poorly born but likeable and hard-working Kirwin, a Catholic lithographer from Cork (splendidly portrayed by Stanley Townsend)?

For a play about painfully sundered allegiances and the collapse of an idealistic alternative society, Prayers of Sherkin is strikingly low on any active sense of conflict. The dramatist has here created a world where essential good-heartedness rages in epidemic proportions, where Presbyterian shopkeepers like the Pearses (Harry Towb and a dryly amused Ingrid Craigie) can feel friendly concern for people of other faiths, and where a fervent millenarian father, such as John, reacts to a daughter's apostasy not with the angry opposition of a Philip Gosse but with a grief-stricken respect for her freedom.

If the primary impulse seems to be lyric rather than dramatic, the affectionate humour, strong charm and elegiac ache of the piece are a safeguard against its coming over as a sanitised account. Barry has a poet's gift for the small, emotionally telling detail. How beautifully he conveys the tenderness towards her motherless niece of Anne Carroll's excellent Aunt Hannah in the down-to-earth, delicate familiarity of her injunction: "You should not rub your eyes, Fanny. The sleep will scratch them." And how tactfully he hints at the comically cranky constrictions of the sect in the girlishly guilty way the other aunt (Susan Engel) can't resist rifling through the gaudy ribbon box in the Pearses' shop.

Barry's preoccupation with what his best critic Fintan O'Toole calls "the ambiguity of belonging" is again evident in this play about a young woman who feels at home on Sherkin despite a double foreignness. She receives, near the end, a vision of Matt Purdey (Ron Cook) who endorses her elopement with the lithographer and tells her that the cries of the gulls she hears calling to her over the water are the voices of her children waiting to be born. So it's not just theatre audiences, but the supernatural, who applaud the existence of Sebastian Barry.

Sundays and Mondays to 15 June. Booking: 0171-928 7616

Paul Taylor