27, Royal Lyceum, Edinburgh

Abi Morgan is on something of a multi-platform roll right now. Between writing the Beeb's enjoyably hokey The Hour and scripting The Iron Lady, the Margaret Thatcher biopic which will be hitting our screens shortly before Christmas with all the force of a jet-propelled handbag, comes a new play for the National Theatre of Scotland.

Mother Superior Miriam and the younger Sister Ursula (“Jackie to her JFK”) belong to a convent in a remote part of Scotland. Even in her eighties, Miriam (Colette O’Neil) remains the fulcrum, her bright, inquisitive mind binding the women together. Ursula (Maureen Beattie) is a torrential force of nature but behind her frantic energy lies doubt and fear.

American scientist Dr Richard Garfield (Nicholas Le Prevost, pictured left with Molly Innes as Ruth) and his team of researchers arrive at the convent seeking to extend the research project they have been undertaking in the US. This involves studying nuns over several years to look for signs of mental deterioration in order to further science’s understanding of Alzheimer’s. Why nuns? Because “as a community you’re easy to track”, explains Garfield. Well, that‘s certainly the practical explanation, but Morgan recognises that the decay of memory and identity offers neat dramatic parallels with this declining vocation. In many respects 27 (the title refers to the number of nuns taking part in the experiment) is a requiem for a rapidly disappearing way of life; twentysomething Audrey (a sparky turn by Emma Hartley-Miller) is the only fresh blood the convent has seen in 14 years.

Ursula realises that it wasn’t God she believed in all along, but the wit, wisdom and humanity of her closest friend

The experiment requires those participating to donate their brains to science after death, a decision which pitches pathology and rationalism against wonder and faith. By the end neither side is terribly sure of its footing, as over five years of annual visits the scientists bring not just their files, Dictaphones and flash cards, but stirrings of sex, love and Mammon, raising more questions than their experiments can ever hope to answer but which can be summarised thus: to meet the world or to retreat?

At the extremities of the group some certainties hold fast. For young researcher Sam (Finn den Hertog), cocky, ambitious and in love (or at least in lust) with his American counterpart Helen (Libby King), it’s all one big abstraction, a matter of statistical analysis leading to published articles leading to a job with a pharmaceutical firm, a bigger car and new wonder pills to peddle. On the other side, Ruth (Molly Innes), the nun with the most resolute faith, questions why science “needs to colonise the miracle” of the brain’s seemingly inexplicable ability to function when all the hard evidence suggests it should have fused long ago.

The slow decline into dementia of Miriam (a fine, utterly believable performance by O’Neil, pictured left with Maureen Beattie as Ursula) humanises the issue, and galvanises a play which starts slowly and occasionally gets bogged down in its somewhat convoluted premise. As her condition deteriorates, so Ursula (played with warmth and energy by Beattie) realises that it wasn’t God she believed in all along, but the wit, wisdom and humanity of her closest friend. With Miriam's mind now “lost”, what remains? As for Richard (Nicholas Le Prevost, rather more stiff than he needs to be), he turns out to be a man obsessed with the chase rather than the kill, less interested in a cure for Alzheimer’s than an ongoing distraction from his own emptiness.

The scientist and the nun meet in the middle, drawn together by their doubts and their willingness to find sanctuary in their own uncertainties. Along the way 27 touches on such givens as the compromises of marriage and the dubious morality of drug companies, but to its credit never loses sight of its core interest in the fundamentally human struggle for meaning. Directed with clarity by Vicky Featherstone, Morgan’s script - drawing on a similar research programme recounted in Dr David Snowdon’s book Ageing with Grace - is witty, emotive, multilayered and grounded in reality (to the point of occasionally becoming soapy and simplistic), portraying religious devotees who are very much part of the real world of frozen Iceland chickens, bourbon biscuits, EastEnders and Countdown.

Merle Hensel‘s set is spare and appropriately chilly, the austerity of the high, grey convent walls lightened by a flash of red roses, a shaft of light from unseen rooms and the shifting seasonal moods displayed on the projected backdrop of the loch. Morgan’s downbeat but quietly affirming resolution suggests that life, whichever path we chose, is ultimately about embracing absences. Without certainty we reach for what - and who - we can and shape our world around it, learning to accept that there is much that we must live without. 

• 27 is at the Royal Lyceum Theatre, Edinburgh until 12 November