What theatrical power survives in William Nicholson's famous, religious tear-jerker! It is, though, thanks to Charles Dance's extraordinarily moving performance that 17 years after its premiere, Shadowlands does not seem a trite piece of religious pleading, on themes of erotic love, suffering and the after-life - when the world's Shadowlands give way to heavenly light.

Dance takes to perfection the real-life role of the Oxford bachelor don, scholar and children's writer, C.S. Lewis, who discovers love in his late fifties. An American-Jewish poetess, Janie Dee's superb Joy Davidman, arrives in Oxford and stealthily steals his heart. The stealing takes time. For Lewis seems an absolute stranger to erotic hankering, marries Joy in a fit of noblesse oblige to enable her to stay in England, and only falls in love when his wife succumbs to a deadly cancer.

Nicholson's idea is to characterise Lewis as one of those sad victims of trauma who fear emotional feeling or commitments, and repress emotions they cannot express. Lewis learns the hard way that the ecstasy of his love leaves him open to intense experience of suffering as well. If only Nicholson had delved deeper into Lewis's psychological make-up and childhood bereavement, suggesting why he had sealed himself off from life and how Joy managed to penetrate his defences, Shadowlands would be a more exciting drama.

He does, though, score nice, comicsatirical points, showing Lewis and his heavily moustachioed brother (Richard Durden's fine shambling Major) basking in their misogynistic, Oxford backwater. Here cloistered, bachelor dons, John Standing waspishly impressive among them, cluster and banter with their elevated repartee. Matthew Wright's expressionistic set, a room enclosed with towering, 14 feet high shelves of books that unfortunately look like dummies, suitably reeks of claustrophobia. Then the back-wall opens up to show figures at tables taking tea. Lewis and his brother arrive to meet the unknown Joy and her young son. Embarrassment soon follows, with Dee's splendidly cool, laconic and unsentimental New Yorker Joy, trying to pierce Dance's C.S. facade. He remains stranded in charm and his smiling detachment.

Autumnally dressed in corduroy, woollen waistcoat and good old English reserve, Dance proves a revelation. He turns himself into a man ill at ease in his own body, adopting an awkward, lop-sided stance and bony gestures that betray the fact. He never cares or dares to catch Joy's eyes. While his brother usually watches over him in rapt discomfort, Dance's C.S. Lewis remains marooned in his own reticence. Dee's charmingly outspoken Joy tries again and again to coax him out of his shell.

He marries her but does not deign to share house or bed. Only when Joy is felled by a terminal cancer does Lewis surrender to feeling. Michael Barker-Caven's slightly sentimental production takes on a golden glow. Dance's C.S. is first transformed by happiness and then when Joy dies, almost deformed. Dance stoops, darkens and shuffles with grief. He makes the worldly process of self-discovery, love and grief both exhilarating and overwhelmingly poignant.