Though Sam Shepard may owe a lot to Beckett and Pinter, his semi-surreal tragi-comedies are distinctly his own – and no straightforward task to stage. In the wrong hands, they can be played as too much tragedy or too much comedy, falling down either side of wonderfully weird.

Not that that’s a worry with Buried Child at the National - the first major London production of Shepard’s 1978 Pulitzer Prize winner in 20 years - with its director’s chair occupied by Matthew Warchus. After all, Warchus was the man who memorably, and role-swappingly, staged Shepard’s Cain and Abel tale True West at the Donmar in 1994 and later on Broadway.

Buried Child, which preceded True West by two years in Shepard’s bibliography, is a more elusive piece. As the playwright himself explained in an interview, “there are many things you may not understand right in the moment of writing, and you may not really understand it actually until years later. Buried Child was like that.”

At its core, in common with the bulk of Shepard’s plays, is a family so inescapably dysfunctional – with more than a hint of incest on top of abuses of just about every other kind - they could give the ancient Greeks a run for their money.

With his giggling girlfriend Shelly (a beguiling Lauren Ambrose) riding shotgun, twenty-something Vince (Sam Troughton) has driven from New York City to rural Illinois in search of his roots after six years’ absence. But, while an initial observation from Shelly tells us that Vince’s homestead is an idyllic-looking Norman Rockwell-esque farmhouse from the outside, Rob Howell’s staggering interior design – in which the drab front room, with its walls and roof gaping open to expose the vastness of an empty backstage, thrusts forward from behind a sheet of rain – confirms its crumbling foundations.

There are more disturbing surprises care of its inhabitants. Neither Vince’s decrepit grandfather (M Emmet Walsh, America’s own version of Michael Gambon, here in full ornery brilliance), his barmy uncle who hacked off his own leg with a chainsaw (wild-eyed Sean Murray) nor even his father (a big but befuddled Brendan Coyle) are able to acknowledge his existence, let alone recognise him. With the return of tipsy but still flinty matriarch Halie (Elizabeth Franz) and her clergyman lover (John Rogan), confusions mount upon confusions, verging on farce, although the air of latent menace never dissipates.

All of the actors in Warchus’ tight-knit ensemble deliver committed and, in the midst of madness, convincing performances, although in true Shepard style, none ever lay themselves completely bare.

In this family, the truth about the past – like the child in the backyard – may indeed be best left buried. Either way, buried or exhumed, it will likely always remain a mystery, as much to the characters as to their author and the audience. Which makes it all the more unforgettable.

- Terri Paddock