<preform>Pyrenees, Menier Chocolate Factory, London</br>The Gigli Concert, Finborough, London</br>A New Way to Please You/Thomas More, Swan, Stratford</preform>

Most peculiar play of 2005? Try this...

April definitely isn't the cruelest month for the thirtysomething Scots playwright David Greig whose work is enjoying a flurry of interest. The Donmar is about to stage his 1999 hit The Cosmonaut's Last Message, the RSC premières his spy drama The American Pilot in three weeks' time and Paines Plough continues its high calibre season at the Menier with Pyrenees, Greig's new four-hander set on the terrace of a hotel in the French mountains. This has gone straight on to my shortlist for Most Peculiar Play Of The Year.

April definitely isn't the cruelest month for the thirtysomething Scots playwright David Greig whose work is enjoying a flurry of interest. The Donmar is about to stage his 1999 hit The Cosmonaut's Last Message, the RSC premières his spy drama The American Pilot in three weeks' time and Paines Plough continues its high calibre season at the Menier with Pyrenees, Greig's new four-hander set on the terrace of a hotel in the French mountains. This has gone straight on to my shortlist for Most Peculiar Play Of The Year.

Everything appears fairly normal and naturalistic at first in Vicky Featherstone's cleverly deceptive production. The terrace is bathed in sunlight and a young woman called Anna (Frances Grey) has just arrived to interview an older, soft-spoken man (Hugh Ross). She is struggling with her tape recorder and he is serenely enjoying the view. However, this scenario proves stranger than it seems. The man, we gather, has no idea who he is. He has been found in the snow, clutching a pilgrim's scallop and a case full of money, with a tabula rasa concerning his past. Anna, sent by the British consul, is trying to work out where he hails from, encouraging him to say if he feels drawn to anything. He declares he is drawn to her. It is evidently mutual. Then, suddenly, the sole other guest, Paola Dionisotti's Mrs Sutherland, interrupts and pulls a photograph out of her backpack. She has been trailing this man for months. According to her, he became discontented with his life in Scotland, faked a suicide and went wild on the continent. His wife wants him back, but the man refuses to accept any of this - initially.

Pyrenees is an offbeat detective thriller where you can never fully rely on any of the characters. Greig is also contemplating the nature of identity - questioning whether we fabricate or can, more positively, reinvent ourselves. What I haven't mentioned is the extremely weird fourth character who is like something out of Strindberg's sinister visions, with one foot in an Absurdist farce. Jonathan McGuinness, as the proprietor, creeps around like some insinuating devil, eagerly watching for falling climbers, pretending he's more than one person, and claiming to be of every nationality under the sun. By the end, he is jabbering about the realm of angels, and the hotel seems to be hovering between the everyday and the spirit world.

I finished up in two minds about this play. Greig tends to spell out his topics rather woodenly and the jolts in tone can feel awkward. But these are deliberate and intriguing, provoking unsettled laughter from the audience as Featherstone's cast deftly switch between the serious, comical and supernatural. In less competent hands, this script could look embarrassingly erratic.

Now to the Irish playwright Tom Murphy whose work is rarely produced in England. Besides boasting a topnotch cast, Gavin McAlinden's fringe production of The Gigli Concert uncannily chimes with Greig's themes. Knocking at the door of a dilapidated office in Dublin, a mysterious Irishman in late middle-age (Niall Buggy) declines to give his name. He might be an unquiet ghost.

Simultaneously, he appears to be a dangerously depressed boozer. He is bored in his marriage and dreams of singing like Beniamino Gigli.

Indeed, he tells his life story as if he is the late, great Italian tenor. The quack he is visiting, Paul McGann's King, is (doubtless significantly) an Englishman who is meant to cure his clients by moving them on to new possibilities. Yet he is in despair himself: drinking and, maybe, madly imagining as well as mirroring his patient - as if battling with his own demon.

Watching this, you realise just how much Conor McPherson's recent play Shining City owed to Murphy. Some of King's more prolix ramblings lost me towards the end, but elsewhere the dialogue is fascinatingly fractured and lyrical, flickering with humour. Buggy is mesmerising, with his moon of a face and ice-blue eyes: mercurially jovial, vulnerable and psychotic. McGann is also on superb form: subtly manic, callously domineering but also caring and a romantic. He copes valiantly too with the hallucinatory climax where he silently lip-synchs to a Gigli aria in a ghostly white light. This is better than many a West End production and McAlinden should go far.

Finally, the RSC's new Gunpowder season boasts a clutch of forgotten gems, each with a still-topical political edge. A New Way to Please You, a black comedy by Middleton and Rowley from the 1650s, centres round euthanasia. A fictional law has been passed to exterminate old people and most of the younger generation, driven by amoral materialism, can't wait to terminate their nearest and dearest. The vicious gallows humour of this could, surely, have made A New Way the precursor of Swift's satirically scorching Modest Proposal (for culling poor children). Unfortunately, the plot is scrappy and director Sean Holmes merely plumps for excruciatingly feeble comedy with no real menace.

Thankfully, the same ensemble are born again in Robert Delamere's thrilling revival of Thomas More, a strong and subtle political tragedy by Anthony Munday, Henry Chettle, Dekker, Heywood and Shakespeare. In the 1590s this play was on dangerous ground and censored because of its hero's Catholicism. Nigel Cooke's More has great moral dignity, humorous warmth, and a hint of wiliness. The play also begins with an electrifying, two-edged portrait of anti-immigration riots in London. More calms the city by pleading for racial understanding. This might be food for thought for our own electioneering politicians.

k.bassett@independent.co.uk

'Pyrenees': Menier Chocolate Factory, London SE1 (020 7907 7060), to 24 April then Palace, Watford (01923 225671), 26 to 30 April; 'The Gigli Concert': Finborough, London SW10 (020 7373 3842), to 23 April; 'A New Way to Please You'/'Thomas More': Swan, Stratford (0870 609 1110), both to 3 November