THEATRE Swaggers BAC, London

Plays about life among the urban criminal classes have abounded in recent years - now and then you find yourself longing for dramas that deal with the down-to-earth, real struggles of people who live in Hampstead and write novels. Still, at least Mick Mahoney can claim to know what he's talking about, having spent much of his youth hanging around with dubious company and getting into trouble with the law.

Swaggers draws on his experiences working in a West End swag shop, the kind of place where you buy bootleg tapes, fake designer clothes, ersatz Cartier watches and computer accessories of doubtful provenance. In Mahoney's version, the shop is a place of staggering wealth - deals are discussed in hundreds of thousands of pounds; vast wads of cash change hands - but it's also a half-way house, a sort of interface between the criminal milieu and the workaday world (among other things, it's a way of laundering drug money). And the staff are similarly caught between two stools, imagining that they're in a proper business, refusing to face up to the fragility of it all - a fragility neatly caught by John Howes's set, with its cardboard boxes stencilled with logos for CK, YSL and DKNY.

So Tess, the manager, dreams of working for a solicitor in Camberwell, but won't make the break because she worries that the law is too precarious. Michael, her boss and lover, lives in a pounds 250,000 house in Hampstead and fondly imagines he's an upwardly mobile businessman. Drop-dead gorgeous Nancy gets her kicks hanging out with gangsters. Only John, a legendary thug just out of jail, and Michael's sister-in-law Dee seem to have any sense of how chancy this way of life is.

There are a lot of things to admire in Mahoney's script: a strong sense of character; an ear for the low-life vernacular; some excellent gags - like John's defence of boxing against the accusation that it causes brain damage ("It's not like they're going to miss out on the guy who's going to find a cure for Aids"). And he paints a convincing picture of the fudged ethic that binds the characters together - paying lip-service to a criminal code of honour and family loyalty that only John really believes in, and to a fastidious sexual morality (thoroughly modern Nancy, with her PVC dresses and psycho boyfriends, turns out to be saving herself for marriage).

The play is marred by some implausible plotting: we're expected to believe that Curly, Michael's superior, has been shot by rival gangsters and kept under armed guard in hospital and nobody in the shop knows anything about it. And Mahoney the director doesn't seem to know how to work the rhythms supplied by Mahoney the playwright; the dialogue often shambles when it should race, a lot of it getting lost altogether. The individual performances are fine - particularly Peter Hugo Daly's amiable, canny John - but they don't mesh together well. All the same, if you did spend your money, you wouldn't feel you'd been robbed.

To 9 March. Booking: 0171-223 2223