At heart the new opera by George Benjamin to a text by Martin Crimp, directed by the playwright's regular collaborator Katie Mitchell, is a straightforward love triangle. The creative team's twist is to present a web of heats and passions through a prism of ice-cool detachment that out-alienates even Bertolt Brecht. In its glacial beauty, Written on Skin grabs the senses but not the soul.

Crimp's Occitan-inspired narrative tells of a ruthless Protector (Christopher Purves, magnificent) who commissions an artist (‘the Boy') to set down his family history in the form of an illuminated book. When the latter attracts the attention of the Protector's young wife, jealousy and horror ensue.

It was a canny move to assign the seducer's role to a counter-tenor. George Benjamin wrote the part of the Boy for Bejun Mehta and plays on the androgynous possibilities of his voice to create a figure whose plausible appeal affects both partners in the marriage. The couple's incompatibility, too, is clearly delineated in the music: the Protector's clean vocal lines convey the certainties of his character while his wife, Agnès, luxuriates in a lyricism that is sensual and sinewy. When the husband rejects her blandishments it is because he can only find arousal in anger.

Barbara Hannigan imbues the role of Agnès with vocal effects of the utmost beauty, even when they transcend the orthodox. The moment when she realises that her lover's heart has been fed to her smacks less of Titus Andronicus that Oshima's Empire of the Senses, so committed is her erotic attachment to the dead Boy's spirit. Minor roles are equally well sung by Victoria Simmonds and the exceptional Allan Clayton, while a quartet of silent actors stalk the stage like seraphic stagehands.

This story of sex and ultra-violence would be lurid were it not framed by so many distancing devices. Crimp and Benjamin's first decision is to set the opera as a visitation on the past by three ‘angels' from the ironic paradise of the present day; their second, rather clumsier in execution, is the use of third-person narration so that every exchange is made oblique. ("A book costs money, says the Boy," says the Boy.) The third intervention is Katie Mitchell's recourse to some familiar directorial tics - Zen-like movement, extreme slo-mo, flattened cinemascope staging, here with split screen effects in Vicki Mortimer's brilliant designs - to create images of transfixing beauty but little emotional connection.

There is no disjunct between the restrained poetry of music, text and production until the crucial moment when Mitchell stages a realistic killing - an act of murder that Benjamin underpins with rough, raw chordal music. Alas, what should be savage is not even startling because the hypnotic mood of the preceding ninety minutes has numbed the spectator's access to volatile human responses. While Benjamin's score haunts the senses (its timeless world adds a glass harmonica and a bass viol to the modern orchestra), much of it is shaped as pure music, not as drama, and it lacks the emotional through-line that allows narrative momentum to grow.

Crimp's text is economical, dense and elegant, only lapsing into the commonplace when he has a modern parallel to push - as when the non-PC Protector declares of his wife that "her still and obedient body is my property". The Boy's heart, says Agnès, tastes "salt, strange and sweet", which is a pretty fair summary of the opera itself, for Written on Skin provided a mesmeric evening of operatic theatre that left me hungry to experience it again. If, ultimately, it's a slightly frustrating work, for all its faults it is on the side of the angels.

- Mark Valencia