In the midst of the culture of tiny studio plays that we now live in (and which has even spread to the West End, with a proliferation of one and two person shows), it seems amazing to find a big, public play for a cast of no less than 21 actors. But it's precisely the kind of play that the National should be getting behind, and marking the opening shot for Nicholas Hytner's new South Bank regime in the Cottesloe, makes a bold statement of intent and even better, of realisation in Peter Gill's totally absorbed and absorbing production.

Owen McCafferty, the Irish writer whose Closing Time was one of the few dramatic successes of last year's Loft season, has moved from that play's beautifully detailed portrait of overlapping lives in a Belfast pub to take on the more ambitious, wider city landscape. Scenes from the Big Picture provides fragmentary snapshots of life and lives in different Belfast locations, some of it again in a pub but elsewhere going from corner shop to offices, street corners to flats.

In a dense piece of impressionistic storytelling that marshals the 21 actors through some 40 scenes, not all characters or stories are as fully realised as others, but the play coalesces around five main couples, three of whose stories revolve around loss and parenting. There's the childless couple, Joe and Maeve Hynes (Patrick O'Kane and Aoife McMahon), where the wife is desperate to conceive but the husband has other thoughts on his mind in the shape of the pub bartender Helen (Michelle Fairley) he's having an affair with. There's the middle-aged couple, Theresa and Dave Black (Frances Tomelty and Dermot Crowley), still searching desperately for the corpse of their son who was murdered 15 years earlier so that they can finally lay him to rest. And then there are the two Foggarty boys, Paul and Harry (Ruairi Conaghan and Stuart McQuarrie), eventually reconciling at their father's funeral.

Two more couples come into sharp focus: the shopkeeper and his ill wife (John Normington and June Watson), and a small-time drug dealer Robbie Mulla (Chris Corrigan) and his drugged-out, abused girlfriend (Kathy Kiera Clarke).

Staged on a busy but mostly bare stage, with the actors sitting on the front row throughout when they're not in scenes, Peter Gill shows why, alongside Max Stafford-Clark, he's the best director of new plays in the country. His production has a wonderful fluency as well as urgency that is finely tuned and textured to underline the sharp realities of these lives.

- Mark Shenton