This first play by 22-year old Lucy Prebble has many of the virtues - and some of the faults - you expect in early work. It tackles tricky subjects, such as paedophilia and teenage psychological disorders, with unselfconscious candour: at the same time, having outlawed instant moral judgment, Prebble can't quite determine what to put in its place.
Like Patrick Marber in Closer, Prebble shows how online chatrooms can easily lead to crossed wires. The screwed-up, sexually knowing 17-year-old Dani (short for Danielle) meets the lonely 38-year-old Tim, who is under the impression he has been in intimate internet conversation with a young boy.
Dani, however, discovers in Tim a wounded soulmate to whom she can relate far more easily than her scatty middle-class mum or the geeky guy with whom she has occasional sex: she even optimistically believes she can help the tormented Tim in his guilt-ridden struggles with paedophilia.
Prebble writes honestly and well, in a manner reminiscent of Shelagh Delaney in A Taste of Honey, about the attraction of outsiderish opposites: the plausibility of the central relationship is confirmed by Dani's teenage mockery of Tim's "dad-rock" and his despair at her rejection of classical literature. But, although Dani reassures Tim that she belongs to a generation that "doesn't judge anything anyone does, only how it's reported", she is sickened when she sees the sadistically pornographic images on his laptop. You are left unsure whether Prebble is telling us that Dani is not as cool as she seems, that Tim is not as reformed as he would wish, or that, in the end, all actions have to be viewed in a defined moral context.
Prebble's purpose may be unclear but she has an instinctive playwright's gift for grabbing your attention and compelling sympathy for damaged people. And all four actors in Marianne Elliott's deft Theatre Upstairs production have a fine neurotic intensity.
Stephanie Leonidas's emotional fragility as the bulimic Dani finds its echo in the defensive irony of Andrew Woodall as the traumatised Tim. And both Kate Duchene as Dani's abandoned mum and Will Ash as her anorak boyfriend exude a strange solitariness as if that, in Prebble's eyes, was the natural human condition. A promising first play.
· Until November 15. Details: 020-7565 5000.
