Lonergan looks back in languor, and with a certain rueful irony, at the generation that emerged at the time of the Reagan presidency. The period is March 1982. And the setting is a one-room apartment on New York's Upper West Side occupied by the drug-dealing, domineering Dennis. But the action stems from the arrival of his chum, Warren, who comes bearing $15,000 he has stolen from his self-made father who has thrown him out of the house. The wily Dennis spends part of the money on cocaine, aiming to get a brisk return on his borrowed capital: the more wimpish Warren hopes that his new-found liquidity will help him entice fashion student Jessica into bed.

As a portrait of a generation of instinctive drifters, Lonergan's play is often very funny. Dennis and Warren fall naturally into a bully-and-victim pattern that disguises a genuine friendship. But the best scenes are those where Warren is left alone with the argumentative, irony-free Jessica. Their preliminary sexual fencing has a wonderfully touching clumsiness. Even better is their morning-after spat when Jessica's post-coital anger and Warren's bumbling helplessness kill any chance of a relationship.

In purely behavioural terms, the play is dead accurate, and Lonergan is not slow to point out that these are all the kids of rich parents who themselves lead pretty messed-up lives. What Lonergan leaves out, however, is the question of whether the Reagan ethos is partly responsible for all this moral confusion. We learn that Dennis's social-worker mother is full of raging impotence at the new economics. But the fame of Dennis's painter-father, and the brutishness of Warren's, seem unconnected to the zeitgeist; and, likeable as the play is, it fails to go the final mile in indissolubly linking private and public lives.

As a result, the focus in Laurence Boswell's production is very much on the performances. Hayden Christensen, looking like a taller Martin Amis, exhibits a fine rangy sulkiness as Dennis. Jake Gyllenhaal as Warren is naturally comic and engagingly defenceless. And Anna Paquin as Jessica combines prim formality of speech with an argumentative sexual ardour. All three are highly talented, instantly beguiling young actors even if Lonergan's study of subsidised social rebels leaves you wanting more.