THEATRE / Bang, bang, dead confusing: Square Rounds - Olivier, National Theatre; Who Shall I Be Tomorrow? - Greenwich Theatre; The Darling Family - Old Red Lion; Lady Aoi - New End

NOT UNLIKE the Sophoclean fragment that formed the basis of his last National Theatre show, Tony Harrison's Square Rounds reaches the stage as the concluding episode of an otherwise unperformed work: The Common Chorus, a post-nuclear reworking of the Lysistrata and The Trojan Women with a chorus of Greenham Common women and an epilogue on the Maxim gun.

In a rueful note to the published text of that play, Harrison acknowledges that the enterprise had been sabotaged by the end of the Cold War. That particular Gorgon shuffled off the stage of history before he was able to look it in the eye. But another presented itself in the shape of Hiram Maxim's invention, which has now evolved from a coda into a full-length and unclassifiably elaborate 'theatre piece' under Harrison's own direction.

Its only link with Greenham is in the casting (21 women to two men); and there is no danger of history foreclosing on them, as their story - that of TNT and chlorine gas - comes to its climax in the First World War (whatever last week's echoes from Peenemunde). Harrison's point of departure is the fact that the inventors of these scourges - Maxim and Fritz Haber - saw themselves as benefactors of mankind. Nitrogen was plucked from the sky to fertilise the shrinking wheatfields. 'I had the noble dream of making Europe green,' Haber says. 'I never intended it (ie nitrogen) for trinitrotoluene (TNT).' Even after the perversion of their discoveries into fertilising the earth with human flesh, the inventors are still claiming they served humanity by bringing a quick end to the war. 'We have got/The Maxim gun and they have not.' Harrison does not actually quote that notorious jingle, but it runs through the show as an unspoken refrain.

Beyond that, I do not know what the show is saying. Harrison ignores the process by which warfare requisitions the arts of peace. Instead, he stages a chemical pageant in which dramatic poetry, music, and magic blind you to the lack of any developing argument. After no less than three introductory chorus marches, Jocelyn Herbert's set (a concentric black and white floor, perfectly realising Harrison's specification for a 'deconstructed top hat') becomes a munitions factory where a wheezy old sweeper-up (Harry Towb) supplies a worm's eye view of the marvels of science, spectrally attended by a shell-shocked mute (Arturo Brachetti). A centre-stage toilet shed launches the topic of fertilisers, and also acts as a magic box for surprise entrances - first by Sara Kestelman's Haber, a Germanic master of ceremonies in top hat and tails (standard costume for the conjuror-scientists) who unveils the innocent chemical past, while the chorus of coughing munitions girls remains on hand as witness to its corrupted present.

There is Justus von Liebig, implacable enemy of the water closet ('England's green and pleasant land will be laid bare,/Because of the contraption inside that cabin there'); followed by Sir William Crookes, prophet of 'redemptive chemistry', transforming base elements into music and all the colours of the rainbow. 'Into the throat that mix of gases goes/and carbon dioxide comes out as Berlioz.' From which point, chemical demonstration diversifies into fashion show, spiritualist seance, and stage magic; and Harrison's virtuoso couplets become inseparable from Dominic Muldowney's music which evokes Messiaen's enchanted forests of high divided female voices and the shimmeringly unresolved chords of the sixth. Even this is only a prelude to the company's Chinese metamorphosis led by Mr Brachetti as a Mandarin magician executing instantaneous costume changes matching the colour of every silk banner he snatches from the air. No such combination of skill and beauty has ever before appeared on this stage.

The magic fades, though, when he explains his mission. It is to inform the erring West that guns and gas were pioneered in ancient China: the implication being that China has now outgrown such atrocious toys. This might pass as a poetic image; expanded, as it is here, into a 10-minute routine followed by a didactic chorus, it seems a gross falsehood. I have dwelt on the positive side of this richly theatrical event. On the negative side, it exhibits stretches of joyless vaudeville caricature (to Muldowney's Weimar vamp), passages where the only function of verse is to find ways of repeating the same point, and a notable shortage of identifiable characters. The big exception is the tragic partnership of Fritz Haber and his suicidal wife (Maria Friedman), who deliver personally impassioned argument through the finest poetry of the evening. They need no magic or pantomime; and when they express their doomed relationship through dance, it is to music by Chopin. A public spectacle; a private drama.

Bernard Kops's Who Shall I Be Tomorrow? at Greenwich is not a patch on his last piece, Playing Sinatra, but there is an irreducible level of imaginative honesty in this author that survives even in this tale of two of life's wounded (she a failed actress, he an ageing and battered homosexual) protecting each other in an uncaring world. There are no surprises here, but neither is there any sentimentality: Kops's hot-line to the scars of childhood and the memory of sexual defeat see to that. The piece is as defenceless as its characters, who are played with truth and considerable fun by Harry Landis and Joanna Lumley - an actress whose habitual gravitation to lame-duck material has this time worked in her favour. She is a treat.

No less truthful is the Canadian Linda Griffiths's The Darling Family, another two-hander in which Gina Landor and Kieron Jecchinis ponder the implications of an unplanned pregnancy before settling for an abortion. En route they chart every fault in the sexual landscape of evasiveness and possession, but without arousing the smallest interest in what happens next. A brief recommendation for Lady Aoi which supplies a rare chance to sample one of Yukio Mishima's modern Noh plays, and arouses the appetite for more.

'Square Rounds', Olivier, National Theatre, (071-928 2252); 'Who Shall I Be Tomorrow?', Greenwich Theatre (081-858 7755); 'The Darling Family', Old Red Lion (071- 837 7816); 'Lady Aoi', New End (071-794 0022).