A TUSCAN farmhouse, four English holidaymakers, a car crash, a gun-toting pyjama-clad stranger and religious intrigue.

No, not the ingredients of a Blair family holiday gone wrong, but God Only Knows, the latest offering from playwright Hugh Whitemore at the Yvonne Arnaud Theatre.

When two couples' quiet stay in the Italian countryside is interrupted by the dramatic entrance of a fraught compatriot with a potentially deadly secret, the tranquil mood and setting are transformed.

With God Only Knows, Whitemore returns to one of his favourite themes - religious faith - and by having the five characters offering differing viewpoints there are opinions that every one of the audience will recognise and be able to relate to.

The role of the desperate Humphrey Biddulph is unquestionably the most demanding, incorporating physical injury, intelligence, uncertainty and paranoia.

The role was Whitehouse's first to be written with a particular actor in mind and Sir Derek Jacobi does not disappoint as the former Vatican researcher who is out of his depth in matters that threaten to shake the very foundations of the Catholic church.

The fact that he is on the run, so he says, from unknown and highly dangerous pursuers is almost forgotten at points, so intense is the reaction to what he reveals.

The play cleverly shows the debate on parallel levels as the theological debate turns to heated argument.

Biddulph's open-minded and analytical approach is too much for the bigoted Charles Minto (David Yelland) whose own viewpoint is whittled down to a wholly unsupportable "You're wrong".

As with their counterparts in the Catholic church, women in the play are weaker participants, Kate Coker (Margot Leicester) offering little concrete argument and Eleanor Mint (Francesca Hunt) even less.

Vin Coker (Richard O'Callaghan) is alone of the four in being swayed by Biddulph's wild claims and theories, but steps neatly into line with the others at the climax when they realise that the allegations may just turn out to be true.

Whitemore manages to compress a series of complex issues into a short space of time by putting diametrically opposed standpoints into conflict over a crucial historical issue, the very nature of which means that it will probably never be resolved.

Calling into question the validity and the subsequent morality of the Catholic church is hardly new, but in God Only Knows some of the more unpleasant truths about humanity are given a frank and full airing in a production that enlightens, investigates and analyses but never confuses.

Olly Hemans

The Herald Arts pages are where you'll find the best reviews of a wide range of theatre and music each week.