Sanctuary, Lyttelton Loft, National Theatre, London

The serpent in the garden

Tanika Gupta's new play, Sanctuary, unfolds in the beautifully tended garden of a London church that is about to be sold off, despite petitions, and converted into a fitness studio – "the new temple to the human body". The beloved grounds will be flooded to create a swimming pool. "All good things must come to an end and we must leave our lovely Garden of Eden, I'm afraid," declares Jenny (Susannah Wise), the thirtysomething vicar. Her description of the place carries an unconscious irony. The biblical Eden predated the Fall, whereas the reconstituted paradise in Gupta's drama shelters a trio of people who have already seen hell.

At the centre of the piece is Nitin Ganatra's wonderfully charming and humane Kabir, the Indian gardener, who – for painful reasons that emerge – has not seen his native Kashmir, nor his young daughter, for 10 years. A daily visitor to his sanctuary is another exile, Michael (Leo Wringer), who used to be a travelling pastor in Rwanda before he fled persecution. Their peace is disturbed not only by the imminent closure of the church but by the unsettling presence of a relative newcomer, Sebastian (Eddie Nestor) who seems to have been a sort of Afro-Caribbean Don McCullin, photographing the world's trouble spots, before booze and disillusion burnt him out.

Surveying the gravestones at the start of the play, Sebastian says this sight makes you feel lucky to be drawing breath and honoured to have been spared. But the play focuses on survival bought at a terrible price, and asks whether there are more compelling moral imperatives than the protection of one's nearest and dearest. "Aren't you ashamed to be breathing?" Kabir asks Michael when the truth about his past comes to light. He had earlier argued that one always survives for a reason. But religion provides Michael with a grotesque form of self-justification: his continued existence, after committing such an atrocity, shows that he has been singled out by God as a kind of star witness to His mercy.

Hettie Macdonald's awkward production cannot camouflage the contrived coincidences (Sebastian chancing upon the man he had been pursuing for years) nor the clumsy plotting (a conveniently mislaid, incriminating Bible) that lead to feverish revelations and a Titus Andronic- us-like climax. We learn too little of how Michael has lived with himself on a day-to-day basis before the piece hurtles into melodrama.

Yet there are, in compensation, some perceptive, finely wrought sequences. Kabir has taken a protective interest in Ayesha (Sarah Sole- mani), a 15-year-old schoolgirl with stepfather problems. But his need for a substitute daughter gets the better of his sensitivity in the excellent scene where he flatly announces his decision to adopt her, and Ayesha, whose least desire is for a second family, rightly takes offence. There's also a lovely humorous set piece in which Kabir advances the view that Jesus nicked all his ideas from the Hindus (surviving crucifixion, apparently, with yoga techniques).

As the female vicar's blunt ex-colonial grandmother, Barbara Jefford brings all her forthright comic authority to a role that shifts tantalisingly between the racist and the racy ("Hey, listen darling, I'm no Christian. I'm simply a bigot"). It's a pity the pivotal vicar herself fails to come to equivalent life in a play which demonstrates that raising the stakes as high as possible does not necessarily lift the dramatic discourse.

To 10 Aug (020-7452 3000)