Fresh Kills, Royal Court Theatre Upstairs, London

I've lost count of the number of orgasms I've witnessed over the years in plays at the Royal Court's Theatre Upstairs. There's almost a comfy feeling of familiarity when you seen one coming, so to speak. Fresh Kills, by the US dramatist Elyzabeth Gregory Wilder, adds two more to the tally.

In the first scene, Eddie (Phil Daniels) - a casual carpenter/decorator with a six-year-old child - is shown being fellated to a more than satisfactory climax by his wife, Marie (Nicola Walker) in a battered old pick-up truck. She has read in a magazine that re-enacting your first encounter is supposed to be erotic, and it appears that this couple's sex life could use some spicing. The sad, comic artificiality of the exercise is emphasised by the fact that the truck is unexcitingly parked in their domestic garage.

By the end of the first act, though, a rather more reluctant Eddie is being orally pleasured in the truck again. This time, the vehicle is stationed by the Freshkills landfill dump on Staten Island and the person taking the very insistent initiative is Arnold (Matt Smith), a 16-year-old whom Eddie has discovered online. But the older man finds that it's one thing to beat off over pornographic pictures of boys on a computer screen and quite another to have to handle the reality. The black joke of the play is that the usual positions are reversed. It's the teenager who becomes the stalker - a nutty nemesis of confusing, seemingly contradictory demands and a satiric challenge to Eddie's efforts to keep his pederastic fantasy world and his paternal Scout-leader self in safe, separate compartments.

Soon Arnold - a poor little rich kid whose banker father paid him no attention - shows up at Eddie's home posing as a deprived youth, and the wife takes him under her wing. The boy strikes a private deal with Eddie: if he's allowed to go to camp with the Scouts, the stalking will stop. Wilder has some droll fun with the tricky line dividing what's considered acceptable and unacceptable in closeness between males. Harangued by his macho cop brother-in-law Nick (John Sharian), who saves him from a conviction, Eddie reminds him that he never minded being sucked off by a team-mate whenever they won a rugby game.

Yet despite a witty, well-acted production by Wilson Milam, I found this piece resoundingly implausible. Would Eddie, communicating online with a boy who is sending him dirty pictures, have taken the risk of revealing that he has a wife and family? And how did Arnold get hold of his phone number and address? At one point the boy jests, "Leave it to me to find the one guy in cyberspace who tells the truth." But Eddie's naivety about the deceptions that are possible thanks to the anonymity of the internet feels forced, a convenience to facilitate the unwanted contact from the teenager. And there's a similar major strain on our credulity in the embarrassing eleventh-hour escalation into melodrama that results in not only one of the characters, but this play, too, committing unmourned suicide.

To 20 November (020-7565 5100)