Dumb Show, Royal Court Downstairs, London

Anyone who has been embarrassed by a tabloid sting (from the actor John Alford and the Countess of Wessex to the DJ Johnnie Walker and the Earl of Hardwicke) would wince at Dumb Show, the wily black comedy by Joe Penhall. Premiered in Terry Johnson's sharply acted production, this three-hander focuses on Barry, a TV light-entertainment star, who is the victim of a set-up by two journalists posing as bank executives avid to look after his account.

Penhall's hacks can't match the exoticism of Mazher Mahmood, the News of the World's investigations editor, who favours the disguise of an Arab prince. Their entrapment techniques do, however, pay a certain homage to his own: the meeting at the five-star hotel; the flattering, lucrative offer; the lulling into an indiscretion; the covert filming; the prompted handover of a class-A drug. But if Mahmood were to treat himself to a night out at the play, I doubt he'd be as happy with its shrewd take on the ethos that breeds both the journalist prepared to conduct morally dubious stings and the celebrity suckers who fall for them.

The play suggests that our confessional culture, with its hunger for self-violated privacy, is actually complicit with these invasive operations. Barry, whose blokey charisma and emotional disarray are powerfully projected by Douglas Hodge, is shopped by his own producer to the hacks - Rupert Graves's stoat-like Greg and Anna Maxwell Martin's young and blandly chilling Liz. Manoeuvring Barry into a position where he will be forced to make a "heartfelt confession'' to a mass-circulation rag is a cheap and effective way to draw maximum attention to the show and give a shrill wake-up call to its declining star.

Even after the monstrous intrusion that has caused his show to be axed and hastened the death of his estranged wife, it's partly the corrupting lure of the confessional culture (with its promise of fees and the chance to make amends) that draws Barry into a further meeting with Liz, the journo with possible story-angles where her heart should be.

Dumb Show is not as trenchant as Penhall's last play, Blue/Orange, but it's only once in a Blue/Orange moon that a drama so taut with dialectical ambiguity comes our way. The new work is weakened by some niggling implausibilities; for example, it's hard to credit that Barry would take quite so long to think of phoning his lawyer.

But Penhall deftly skewers the outrageous piety and hypocrisy of trial by entrapment (cheap tabloids are not best placed to accuse others of being bad role-models), and I enjoyed the comic inconsistency with which Greg, while presenting any objection to his grubby work as an affront to free speech, can concede privately that their victim is "just an idiot. It's not against the law to be an idiot." I also treasure the moment when soft-soaping Liz signally fails to impress Barry with the idea that what she had really wanted to be was a music critic.

To 9 October (020-7565 5000; www.royalcourttheatre.com)