Tender, Hampstead Theatre, London

Now I see why I'm such a wallflower. Tash, a girl with a string of mindless jobs and a squalid flat, drinks too much, takes too many drugs, and embarrasses herself and her friends. Yet a lot of the men she ridicules to their face take her home, and one, a doctor, even says he loves her. Hen, her best friend, listens to Tash's relentless hatred, only saying: "You make it hard for people to like you.'' Even when Tash sleeps with the pregnant Hen's boyfriend, and taunts her with his other infidelities, Hen says: "I want to love you. But you make it hard.'' See, that's my trouble. I'm too nice.

Tender is one of those limp meditations on relationships that the Hampstead Theatre goes in for. Abi Morgan's drama consists of the sort of dialogue that doesn't seem to say very much, but, on examination, says even less. Besides the doctor, Tash sleeps with her boss, a marketing man (Sean O'Callaghan), who shows her how to video people in a supermarket. The marketing talk is beyond belief, as is the doctor's bathetic outburst while shopping: "You should know better than to tell people to drink more, to eat more, to live more, to buy more... What happened to love?'' There's also Gloria, whose husband of two decades vanished the year before. We discover that he's now a cleaner, lives in a hostel full of drunks, and has never been happier.

Morgan's language can be penetrating and clever at times. Tash sulks that Hen, in having a baby, is "choosing to settle. You're having your future now''. Irate at the constant change of personnel at the missing-persons bureau, Gloria says, "It isn't exactly a good advertisement, is it? 'Missing persons' – every time you show up the staff have disappeared!''

Generally, the dialogue is banal-precious, constructed to keep us from learning much about the characters and full of false notes. If Hen and her boyfriend badly need money, why is she working without pay? Why would a woman, after spending the night with a man, say that she used a feminine hairbrush which had "a lot of blonde hairs and I'm dark so if she sees, whoever she is, can you apologise''? Why would a young, educated, happily married woman commit suicide because she lost her job? How could a loving husband not know his wife isn't a natural blonde?

The production is of a much higher quality – Anthony Clark's direction, Niki Turner's severely chic set, and the acting, especially by the dishy O'Callaghan as a desperately lonely man and Nicola Redmond as Gloria are all first rate. It's a shame there's nothing inside their exquisitely wrapped package.