Shadowlands, Wyndham's Theatre, London

Joy and pain in the darkness

As well as being the creator of the Narnia stories, CS Lewis was a professor of English literature and a combative Christian apologist. At the start of William Nicholson's moving play Shadowlands, this bachelor don delivers a lecture to the audience on the meaning and value of pain. "Pain," he argues, "is God's megaphone to rouse a deaf world." Rouse it from what? Answer: the deluded dream of self-sufficiency in an existence where all is apparently well.

Lewis's imagery suggests that human beings are the raw materials of the deity's projected art work. The hammer blows of fate, he contends, thumping fist on hand, are simply the strokes of the Sculptor's mallet bashing us into perfect shape.

At the beginning of the second half, Lewis repeats this talk, but the robust conviction that had informed it first time round sounds as if it is beginning to crumble. Suppressed tears seem to be dragging the lines from their rectilinear certainty. His manner trembles on the tremulous. This is because of the momentous change that has happened in the interim.

Behind him, there are hospital screens. Behind them, writhing in the agony of bone cancer, lies Joy Davidman, the Jewish-American who fell for him through reading his books and letters, infiltrated his life (he was in more than one sense "surprised by Joy") and reawoke in him a capacity for love and vulnerability that had been in moth-balled abeyance since the cruel death of his mother (also from cancer) when he was eight.

Life might seem to be imitating the Goodbye Mr Chips formula: repressed middle-aged academic brought to late-flowering bloom by an extraordinary woman who is then untimely wrested from him. But the female in this type of scenario is usually a blatant contrast to the man: instinct complementing intellect. In the case of Lewis and Davidman, though, the gratifying twist is that she is a very sharp thinker, too. There's a lovely scene where she unearths the buried assumptions in one of Lewis's obiter dicta, and another where she fingers with pin-point accuracy his tendency to caricature an opponent's argument by summarising it in a dismissive image.

Janie Dee gives a beautiful, pitch-perfect performance as Joy in Michael Barker-Caven's wrenching but emotionally tactful production. It's Joy's witty courage and luminous love for the writer that come through with piercing strength in Dee's portrayal.

Whether routing misogynist, overgrown-schoolboy dons ("I need a little guidance. Are you being offensive, or merely stupid?" she asks one) or crisply summarising the reasons for Lewis's physical awkwardness with her in a sympathetic way (he doesn't want to hurt her), she projects Joy's courteous American honesty and directness with great humour and accuracy. She credibly incarnates a person who, even as she sinks into her final agony, can see things from a dryly comic angle. Noting that she's Jewish, broke, divorced and dying, Joy asks: "Do I get a discount?"

Dee has the shtick down pat, and shows you the generosity with which the character deploys it. She's always her own woman, but others come first. She likes precision, but she knows that you have to open yourself to being hurt.

At first, I thought that Charles Dance was too tall, dishy and romantic a figure for Lewis, and by temperament he seems concessive, whereas the Prof was defensively pugnacious. But Dance is unbearably affecting as he traces Lewis's battles with grief and God. Joy leaves behind a young son who presents Lewis with an image of his own eight-year-old self unable to cry after his mother's death.

I loved the way Dance, who wrings your heart, refused to milk the climactic scene where he and the boy break down together, clutching each other for mutual comfort in an embrace that also includes the bereaved little Lewis.

And the question of pain? If you leave out God, you have to ask whether Joy would do it all over again and ponder the implications of her almost certainly affirmative answer.

To 24 December (0870 040 0046)