MUSIC / The mark of the beast: The Lighthouse, Queen Elizabeth Hall

Gilbert and Sullivan's Mikado was the young Peter Maxwell Davies's first musical experience, so it is no surprise that his opera The Lighthouse includes a banjo ballad, a parlour love song, and a Sally Army chorus complete with tambourine. Coming from Davies, these Victorian stylisations are no less striking for the dark sublimations they contain: of murder, unnatural love and corrupt religious zeal.

In this lighthouse, as on the Marie Celeste, there's an insoluble mystery - the unexplained disappearance of the three keepers. And in their fate lies the work's thrust, its resolution framed in terms of the psychological thriller. The Beast, whose mark is on us all, had run amok and the keepers, each submerged in his own dark past, had fallen victim to its curse.

A masterly blend of atmosphere and character, with a form that deftly sidesteps the issue of what actually happened to the keepers, Davies's powerful score avoids both the cliches of the whodunnit and any hint of melodrama.

At the South Bank on Tuesday, the three male singers - Philip Creasy (tenor) as the sexually frustrated Sandy, Henry Herford (baritone) as the thief and murderer Blazes, and Kelvin Thomas (bass) as apocalyptical Arthur - switched roles from doomed keepers to puzzled inspectors at the flick of an oilskin. Through an ever tighter spiral of flashbacks, the work fed back into itself. The ending revealed the official cover-up, yet, as the music that began the act returned, it was clear the cycle of terror could begin all over again.

The depiction of the keepers' moment of crisis was the only low point in this otherwise splendid production by Music Theatre Wales; but perhaps only a coup de theatre could have saved them here. Elsewhere, the strong cast under Michael McCarthy's direction gave a gripping performance that kept me on the edge of my seat.

Marooned on the vast expanse of stage within a metal cell made of four vertical girders, the victims turned savage before your eyes. Vocally, they were a well-matched trio, their words audible most of the time, or, when obscured, their sense carried along in the general sweep of things. Fluent, disciplined playing from the instrumental ensemble, conducted by Michael Rafferty, maintained the musical thread of suspense, with some surprises. Pip Eastop on horn and trombonist Simon Wills bore the brunt of the assault, not least as the voice of the foghorn. Other sea sounds - gulls, wind and waves - were impersonated by Kate Lukas on flute and Roy Sinclair on timps.