Joachim Herz's 25-year-old production of Madame Butterfly for Welsh National Opera has proved a supreme vehicle for successive sopranos to create their own interpretations of the title role. Nuccia Focile's Madam Butterfly is arguably even stronger than when she first sang it two years ago. Her Cho-Cho-San seems a fragile young thing, infinitely breakable, but underpinning her whole existence is an iron will, forged from the moment her father committed hara-kiri. It means that Butterfly's flirtation is as much with death as it is with Lieutenant Pinkerton: even in love, her behaviour has the mark of an obsessive.

The Sharpless of Christopher Purves is as rich in dramatic detail as in tone. He brings to his scenes with Butterfly a profound compassion that stems from his witnessing her at the Christian mission, where, in her attempt to conform to the American ideal, she effectively sacrifices the respect of her family. But, in Sharpless's infinite concern that Pinkerton treat her gently, there is also a strong suggestion that in his way he could love her, too. The musical chemistry here was definitely between Focile and Purves.

As Pinkerton, Stephen O'Mara is crass and callous, with the swagger of self-satisfaction but none of the vocal charm essential to sustain the emotional credibility of the role. His sound is constricted somewhere at the back of the throat. As the Bonze, Vassily Savenko similarly fails to pass muster: he has the stature but little else to commend him. And, while Claire Bradshaw's Suzuki matches Focile for commitment, she would do well to curb the histrionics.

Conductor Julian Smith's ardour has hardly dimmed over his long association with the production and, in terms of their ensemble work, the company continues to shine. But it is Focile who shines brightest, carefully husbanding her resources so that in the final scene, Butterfly's destiny is tragically but gloriously fulfilled.

· At Sadler's Wells, London EC1, on Wednesday and Friday. Box office: 020-7863 8000. Then touring.