Christoph has a secret obsession. He collects stamps and feeds his habit by stealing rarities from the local museum. He's helped by his girlfriend Francesca, who creates a diversion while Christoph snaffles whatever he craves. She has her own addiction: spending the money that Christoph gives her on the designer goods that they sell in their day jobs.

That is the basic story of Edward Rushton's latest opera: a breezy, fluent chamber work in 30 snappy scenes which the Opera Company unveiled in Birmingham before taking it to the Bregenz festival and on a British tour in the autumn. It is a comedy, and Dagny Gioulami's libretto never takes itself too seriously. Even the scenes after Christoph's inevitable arrest, where the roots of his obsession are explored by a psychologist and a police officer (himself a closet stamp collector), have an over-the-top satirical edge.

Musically, though, it doesn't always seem punchy or vivid enough. Placing the 10-piece ensemble behind the stage doesn't help the sense of immediacy and makes it difficult to focus upon the details of Rushton's instrumental writing, especially the extraordinary textures he obtains from percussion, four strings and a choir of five clarinets. His vocal writing, though, is assured; Darren Abrahams as the driven Christoph and Anna Dennis as his grasping girlfriend are outstanding, and so too are Phyllis Cannan, Richard Burkhard, Louise Mott and Paul Reeves in a gallery of cameo roles. John Fulljames's production, on a set by Soutra Gilmour made entirely of designer carrier bags, is punchy and economical, though how much substance there is beneath - whether or not it is a serious exploration of the mania of collecting - remains an open question.

· At the Linbury Theatre, London, September 19, 21 & 22 (020-7304 4000), then touring.