Death becomes her

Lauren Ambrose has no idea what her new play, Sam Shepard's Buried Child, is really about.

'I agreed to do it because when I read it, I didn't understand it,' she says over a hasty lunch at the National Theatre, where she is currently deep in rehearsal. 'Now we are previewing and I still don't understand either the play or my character.'

Buried Child is, in fact, one of the more accessible of Shepard's typically enigmatic dramas. First published in 1978, it is set within a barely functioning Midwest family so screwed-up by their past that they no longer recognise their grandson, Vince, when he comes to visit.

Ambrose plays Shelly, Vince's hippy teenage girlfriend, who bears witness to the family's nasty secrets when Vince abandons her in the house to go and get drunk. It's odd, extremely funny and very black.

As such, it is perfect territory for Ambrose, better known as the teenage daughter Claire from Six Feet Under, the hit show about a family funeral business, now in its fourth series on E4. 'My friends look at me strangely when I tell them the title of this new play,' grins Ambrose. 'They're like, "Lauren, there's a pattern emerging here".'

Ambrose, 26 and three years married, appears to be as stable and calm as her on-screen counterpart is wild and vulnerable. That said, she relishes playing emotionally reckless teenagers.

'It's such an interesting period of your life, being a teenager; you find out all these things for the first time,' she says. 'I want to play this age for as long as I can.'

Buried Child is her first piece of theatre for some time, as Six Feet Under's production company has 'bought' her for six years. Ambrose is not complaining: 'I was able to buy a house because of the show,' she says.

However, I suggest that building your career on TV in America is more creatively satisfying than in Britain, given America's reputation for ground-breaking TV.

'But you have Cosmetic Surgery Live,' she says drily. 'I came across that flicking through the channels in my hotel room the other night. Horrendous. Some images you can't forget.'

The only problem with being in London, as she sees it, apart from missing her husband, is that she hates being away from America during such a significant election. 'I feel so guilty being here!' she says. 'I should be in New Hampshire or Ohio or somewhere, getting people to vote.'

This is clearly something she feels strongly about: as we speak she is in the middle of trying to sort out her absentee ballot and she talks at great length about the 'outrageous' system in Florida that prevents people from voting if they have a criminal record. She has even recorded a five-minute commercial urging people to vote.