THEATRE / Double or quits: Paul Taylor on Brian Friel's Philadelphia, Here I Come] at Wyndhams

The protagonists of certain plays are beside themselves in more ways than one, a fact spelt out in the title of a recent drama by Sarah Daniels. The middle-aged, middle-class heroine of Beside Herself (1990) is orbited throughout by a tense, asexually waif- like woman, dressed, although she's an adult, in a little girl's frock and an Alice band.

Unseen by the rest of the cast, she is the heroine's shadow-self, the damaged, sexually abused girl the grown-up has tried to suppress. Beadily monitoring the older woman's behaviour, she pounces on its evasions and hypocrisies and blurts out embarrassing truths. Their pained double-act is a brilliant dramatisation of the split found in many abused women - the empty, smiling husk going through the motion of adult life, while the unhealed self dreams of anarchic revenge.

An earlier and singularly successful use of this technique can now be seen in Dan Crawford's glorious revival of Brian Friel's Philadelphia, Here I Come], which has just transferred from the King's Head to Wyndhams. Friel is sometimes said to have borrowed the idea from Eugene O'Neill's Days Without End, but that stiff, portentous play which has split selves kitted out with masks, ends up with alter ego all over its face, whereas Friel deploys the convention with a wonderful suppleness and humorous humanity.

The play shows us the public and private selves of the 25-year-old Gar O'Donnell on the eve of his leaving Ballybeg and his father's store for a new life working in a hotel in Philadelphia. At first, though, you would never guess, from his widowed father's conversation and behaviour, that even the slightest disruption to the old routine was in the offing. The relationship between the two men has silted up with mutual embarrassment and only verbal exchanges of the most banal kind are possible. It is into this bleak communication gap that Friel interposes Gar's shadow self (part id, part conscience) who has a gift of the gab that can fill and send up any long silence.

Crawford's production has manifold virtues, but the key to its success lies in the perfect physical casting of the two Gars. With that faintly superior glint from widely spaced, forward-staring eyes and a face that seems like a tabula rasa on which any emotion can be provisionally caricatured and then rubbed out, Brendan Coyle's Private Gar forms an intriguing contrast to the Public Gar played by Jonathan Arun, whose handsome features italicise in neon whatever he happens to be feeling at the time. Coyle has the brilliant knack of being able to stay cool and above-it-all, while being hilariously antic. Gawky, tongue-tied, and with none of his counterpart's freedom of manoeuvre, Arun suffers through the predictabilities of his final tea a deux with his father - except that, to us, it's a trois, with Coyle giving an unctuous mock-commentary on the paternal preparations and then turning the couple's resolutely sparkle-free non-conversation into an English language lesson. What saves the satirical high jinks from any hint of gratuitous cruelty is the fact that they palpably spring from a desperate longing for communication. Gar wants to be told not to go.

The acting is uniformly excellent. Ruairi Conaghan, Aiden Dooley and George Heslin are uncomfortably authentic as Gar's friends, lumps of village lads suffering from galloping virginity who bolster each other's illusions that they're lady-killers and have to bluff their way out of an understandable jealousy that Gar is making an escape from their backwater. As the mordant, kindly housekeeper, Madge, Pauline Delany continued to be extremely moving, though a slight tendency to drag out and overmilk the sentimentalities of the last scene has crept into her performance since the King's Head opening. Eamon Kelly's father, though, is as splendid as ever, creeping gingerly round his son's last hours in Ireland and pitiably unable to display his heavy heart.

Philadelphia, Here I Come] continues at Wyndhams, London WC2 (Box office: 071- 867 1116).