Since its impressive opening at the Cottesloe in London's Royal National Theatre last April, Max Stafford-Clark's perfectly clear production for Out of Joint and the National has shaken down and shaped up and been even further enriched by a deepening and broadening of the characterisations and performances. What is possibly Sebastian Barry's best play is now a major and deeply-moving work of theatre in which Sinead Cusack's performance as the author's alcoholic grandmother is at once toweringly brave and chattily accessible and left this reviewer in tears at the close.

We discover Mai O'Hara (nee Kirwin) at the age of 53, dying of alcohol-induced liver cancer, demented by a mixture of guilt and morphine so that she is unable to recognise her daughter or hear her husband's apology for accusing her of being, through her drinking, the cause of the death of their seven-week-old son, Colin. She retreats in her scrambled mind to the old certainties of Dada with cakes in his pocket and the times when, in the wonderful garden of Grattan House, where they lived, she would, her hand in his, assert that the violets were blue, blue, blue.

But before that final retreat into terrible death we have learnt in a series of memories and hallucinations on her death-bed of her youthful vitality in Galway, her unfavoured and unsuitable marriage to handsome Jack O'Hara, her eager grasping of destructive alcohol as an anaesthetic to dull what has become for her the pain of living in Sligo, a life from which she wants (but does not get) rescue. At the end we weep not just for her death but for her life. Mr Barry has portrayed his grandmother honestly, not with the arrogance of sympathy but with the humility of empathy, and Ms Cusack has done precisely the same with his beautiful words and her courageous, exquisite and utterly unpretentious characterisation and performance, effectively supp orted by Andrea Irvine, Nigel Terry, Catherine Cusack, June Watson and Harry Towb. Alas, they are here for only two weeks. They must come back again.

Continues until Saturday, September 26th. Booking: (01) 874 4045 and 874 6042