There's a fascinating novel by Mary McCarthy called Cannibals and Missionaries in which terrorists hijack an Iran-bound Boeing which happens, handily for them, to have a tourist party of US art collectors on board.

What is meant by the value of art is put to a revealing test as the captors offer to fly a collector out after her Vermeer is flown in, say, or to let another leave the moment his Cezannes arrive. In tandem with these transactions, the book makes its brilliantly ironic (and debatable) contrast between cultural exchange values and the lethal purity of terrorism which is 'the art for art's sake of the political realm'.

At the end of the first half of Pentecost, David Edgar's wonderfully thought-provoking new play, art once again becomes a bargaining chip in a hostage situation. A multinational group of armed and desperate asylum-seekers, who have crossed the border into an unnamed, post-Communist state, raid and occupy an old church and are soon brought to realise that their human prisoners may be of far less value to them than the medieval fresco newly exposed on the wall of the church.

For what common sense would say must be the work of a later artist who'd either seen or heard report of Giotto's The Lamentation over Christ, may infact have been the inspiration of the Giotto, anticipating its use of perspective by several decades. As an art find, this could be up there with the unearthing of Pompeii.

Pentecost is a richer piece than the McCarthy novel in part because the world is a more confused place ideologically than it was in 1979, when that book was written. With great wit and empathy, Edgar uses the fresco, its questionable status and the competing ethnic, national and religious interest-groups who flock round it, as a piquant vantage point from which to look at the ironies and agonies of post-Communist Eastern Europe and at conflicting attitudes towards art.

For Gabriella Pecs (Jan Ravens), it matters terribly that the fresco pre-dates Giotto since it could then function as a huge boost to the self-esteem of a nation hyper-conscious of having been a Turk-dominated wallflower during the March of European Civilisation. To the slickly philistine young Minister of Culture (Glen Hugill), who talks in bullish American-English to the Western art experts, it just represents a tourist gold-mine.

From different motives, neither care about the consequences of taking the fresco down and relocating it in the National Gallery. But the restoration has already caused the removal from the wall of the names scratched on it when the building housed Nazi torture victims. What price 'eternal' values, if restoring an art work obliterates the historical record as a face-lift does? The upholder of that notion quickly changes his tune, though, once a gun is pointed at him in the looser, less impressive second half.

Ironically, given the title, the lingua franca is English as a second language, post-Communism's hard currency. Linguistic ambiguity, whereby the same word can mean quite different things in two different languages or two diametrically opposed things in the same language, eventually supplies the wonderful, culturally revolutionising solution to the fresco's dating riddle. I admired the way Edgar even found a visual equivalent in the iconography to this verbal pointing-in-two-directions while feeling that it was a shame that he had had to invent a language where there was one ambiguous word for 'to' and 'from'.

Rarely does either the play or Michael Attenborough's potent production get bogged down in the huge mass of intricate detail. If at times you feel that the clever script is so pleased with itself that it doesn't need any more fans, you would have to agree that it has a very great deal to be pleased about.

'Pentecost' at the Other Place, Stratford-upon-Avon. Booking: 0789 295623.

To 27 Jan (Photograph omitted)