THEATRE / The ghost of an idea: Paul Taylor reviews Hammett's Apprentice

What do you call a girl who keeps hallucinating visits from one of the Tolpuddle martyrs? Tolpuddled, perhaps? That's the unusual state in which we find Mary (Gina McKee), a lanky, unstable Geordie reading physics at Cambridge and the central character in Hammett's Apprentice, Kevin Hood's new play at the Royal Court's Theatre Upstairs.

'If this is something to do with Rag Week, forget it,' she snaps when this elderly 19th- century figure first appears. Precisely what it is to do with takes some time to materialise, though there are early clues. For a start, the martyr in question, James Hammett (Ewan Hooper) reveals that he was arrested in mistake for his brother John and that he maintained a self- sacrificial silence when sentenced to transportation. The theme of substitution and secrecy is thus broached.

It turns out, as well, that James had apprenticed Mary's great-great-grandfather. So the inescapability of family comes into it, too, a feature not calculated to appeal to Mary, a girl who enjoys telling her mother that she lost a job in a Kentucky Fried Chicken outlet through vomitting in a family bucket.

In fact, after you've sat through James Macdonald's beautifully acted production with its expert shifts of mood and poetic modulations between scenes, you may well feel that the figure in the carpet that emerges is not so interesting as some of the quirky detail sprinkled across it.

Also, Hood's thematic pattern requires incidents that depend on conveniently uninvestigated aspects of the character. So that history can threaten to repeat itself, Mary, the illegitimate product of a quickie after a rock concert, is called upon to lose her virginity to a stranger after a party. She can't remember anything about this, being high on alcohol and anti-depressants. Does the phrase 'date rape' enter the head of this highly educated feminist? Not a bit of it, she drops out of Cambridge and camps on the man's floor.

Mary, like James Hammett, has been a substitute, a replacement for the baby her grandmother lost as a girl. The linked themes of trade unionism and women's sacrifice to improve their successors' lot, only, however, come into shaky focus.

It's the odd-ball mood- scenes that work best, as when Mary, suspended mid- air after flinging herself off a balcony, is taken to task by her gran's ghost for damaging the clematis. The dialogue has inspired patches, too. When her mum finally tells her the identity of her father, there's a wonderful dented defiance in the line, 'He may be a postman now, but he was an anarchist in 1973 . . .'.

Royal Court, London SW1 (071-730 1745)