"Tradespeople are like gardeners, you can't trust them," says Lady Lucy Angkatell dismissively, as she waves an unsatisfactory lobster in the air. It soon becomes apparent that snobbery reigns supreme at The Hollow, the country house where Lady Lucy (Kate O'Mara) lives with her husband, Sir Henry (Tony Britton).

But it's not only tradespeople who are criticised. Take the Cristows, for instance, who have been invited for the weekend. "Gerda's like a puzzled cow," Lady Lucy declares. Mousy Gerda (Louise Faulkner) comes complete with husband John (Ben Nealon), a rather unpleasant surgeon: "I hate sick people although they've made me a lot of money". Apparently patients get in the way of his research and his nasty temper must be distinctly unappreciated in the operating theatre.

Various other members of the Angkatell family also gather for the weekend. They're a strange, rather inbred lot they all seem to be second cousins to each other. There's Henrietta (Tracey Childs), who specialises in making erotic sculptures and having passionate affairs. There's abrasive young Midge (Chloe Newsome), who actually works in a posh London hat shop. And there's Edward (Simon Linnell), a jumpy, ineffectual sort of chap, who has never had to earn a living, and has never managed to acquire a wife.

The Hollow at Cheltenham's Everyman Theatre is by Agatha Christie, so you can be sure that someone will end up dead. But who? A member of the Angkatell family? Or will it be one of the Cristows? The whole of the first act (exactly one hour long) passes before a gunshot rings out, and someone collapses onto the floor.

Much of that first hour passes in rather turgid chitchat but you've got to keep listening, of course, in case vital clues are being dropped into the conversation. Even so, there's considerable pressure on the director (Joe Harmston) and his cast to keep the tempo moving along you certainly realise that the current episodes of Poirot on TV have been expertly tightened up by their scriptwriters. Not surprisingly, the most experienced cast members are the best at keeping you interested. Tony Britton's Sir Henry appears to be an amiable old buffer, but it soon becomes apparent that he is as sharp as a needle underneath. But the star turn is undoubtedly Kate O'Mara's Lady Lucy. She even risks sending up the whole Christie genre at times: "The trouble with murder is that it does upset the servants so," she observes cheerfully.

This is the first production from producer Bill Kenwright's new Agatha Christie Theatre Company. Younger theatregoers could find it heavy going, but a packed Everyman attested to the fact that there is still a big audience for Christie served up in largely traditional style.