Theatre: Saturday Night's all right

EACH TIME it's something different. When Nik Cohn wrote his article for New York magazine it was a figure glimpsed standing in a doorway, a symbol of machismo, a street aristocrat. When Robert Stigwood produced the movie it was about John Travolta and the Bees Gees. Twenty-one years on, with the opening of the stage musical, Saturday Night Fever is about Arlene Phillips.

The choreographer of scores of pop videos and founder of Hot Gossip, Phillips has turned Saturday Night Fever into an unashamed disco musical. If you wanted to compare it to the film you could say it doesn't have Travolta, the gritty sense of working-class Brooklyn or the Bee Gees singing their own songs. The nicest thing you could say about the plot is that it's largely been ditched.

I was grateful for the losses. When you go to the London Palladium you don't want to spend a lot of time sitting round the Manero family table while Tony is rude to his mum over the spaghetti bolognese. When you're at the Palladium you want to get down to the disco and fast.

In the movie, Travolta chose to film his dance sequences in short takes (unlike Astaire) and the extras bopping round in the background were pretty average. Here, we get whole numbers - and singing as well as dancing. It's high-energy stuff. So long as we're in the disco the show never flags.

After Phillips, the next person doing a big number is designer Robin Wagner. His spectacular designs for Odyssey 2001 include a ceiling which descends like the bottom of a spaceship, with swirling lights and jets of dry ice - a moment that rivals the helicopter scene in Miss Saigon. The back walls have red bars that pulse up and down like the amp monitors on a hi-fi. The nifty aspect of the disco scenes is that Andrew Bridge's lighting - rather than hanging above the action like an alien barrage - is built into the set. From the costumes to the floor lights, this is a big, splashy, colourful show.

Turning this particular movie into a musical is a tricky task because the Bee Gees wrote pop songs not dramatic songs. The show goes belly-up outside the disco, where the numbers are delivered as solos. When Adam Garcia's energetic and boyish Tony gets rejected by the older Stephanie - a coolly impressive Anita Louise Combe - he breaks into the new Bee Gees song that Celine Dion sings on Let's Talk About Love: "So this is who I am/ And this is all I know/ And I must choose to live." As lyrics go, they could go pretty much anywhere.

The high point is the competition in the disco. It works better here than in the film. Yes, we've exchanged grit for fluff: but this is just right for anyone who wants a little high- adrenalin vacuity in their lives. Judging by their applause on the first night, Fergie, the blokes from Abba and Sir Tim Rice are just those sort of people. If you're tempted, then book now, before the dancers go stale.

Sarah Kane's first play, Blasted, had the luck to offend enough critics to catapult her into the "controversial" category. Even Newsnight did an item on it. That succes de scandale ensures Kane's new play Cleansed opens in the heart of the West End. Blasted illustrated - among other things - how far stage direction has progressed in the last 100 years. When Gwendolen is disturbed in The Importance of Being Earnest, "she bites her lip". When Cate is disturbed in Blasted, "she bites his penis as hard as she can".

Glance at the text of Cleansed and you'll see a striking development in Kane's work. The ratio of stage directions to lines of dialogue has increased exponentially. Sometimes a page will contain one line of dialogue - a single word, even - for every five lines of stage direction. Few people can match Kane for vividness in this area of her craft. "He takes Carl by the arms and cuts off his hands." "The rats carry Carl's feet away." "Grace touches her stitched-on genitals." The dialogue is a bit disappointing: "I'm in love with you." "How can you be?" "I just am."

Director James Macdonald and designer Jeremy Herbert stage these images with undeniable flair - a queasy, stylised mix of the violent and the antiseptic. All this raises the issue of whose show it is we're watching. The script itself might take 15 minutes to read out loud but Macdonald's showcase production runs for an hour and 35 minutes.

The sequence of events involves social outcasts in an institution - described as a university - who are kept inside the perimeter fence where they are brutalised and murdered. A brother and sister (Martin Marquez and Suzan Sylvester) have committed incest. Two gays (James Cunningham and Danny Cerqueira) are in love. A delicate, shaven-headed figure (Daniel Evans) loses his mind and kills himself. In charge, there's a sadistic pseudo-doctor (Stuart McQuarrie) who goes to peep shows where he falls in love with the dancer (Victoria Harwood).

Threading through all this cruelty is the search for love. Beyond that, it's hard to grasp what the uncompromising Cleansed is about: the brutalising impact of conventional sexual roles; society's fear of difference; social pressures legitimised through education; the sexuality of cruelty. Perhaps. But Kane's hermetic essay - macabre and opaque - blocks out imaginative involvement from the audience. While the cast are excellent, we learn little through watching them. Half the time the play could be an installation in an art gallery.

By contrast, Robert Holman's subtle and multi-faceted Bad Weather, which premiered at Stratford on Thursday, travels without any great fuss in wholly unexpected directions. It opens on a Middlesbrough council estate where, in Ashley Martin-Davis's canny set, corrugated sheets, National Front graffiti and a litter bin sketch in a grim cityscape where taxi drivers refuse to take rides. It moves - via tower-block flat and the Deerbolt Young Offenders Institution - to a chateau near Reims.

A man has been beaten up outside a Chinese in Middlesbrough, and Jamie, played with vulpine despair by Ryan Pope, goes to prison while his mate, Luke, who actually did the kicking, remains free. Paul Popplewell's Luke starts out an insolent aggressor and transforms across the three hours into a impish charmer handing round the tossed salad.

The catalyst for change is the arrival of the old French nanny, Agnes, who once looked after Jamie's mum. As Agnes, Susan Engel brings a cool Continental watchfulness to the emotional tangle. The complexity of her own relationship with her former charge, Kay, played with a plaintive intelligence by Susan Brown, deepens as this outsider attempts to help Jamie by redeeming Luke.

There's more: Kay has an affair with the one juror who spotted the injustice at the Crown Court trial, the bulky, sensitive Barry Stanton, while her son's girlfriend, Rhona (a candid Emma Handy) is pregnant. Director Steven Pimlott handles these myriad strands with a sure, uncluttered eye. He gives each character an equal weighting that draws out strong performances. As the play moves between prosperity and poverty, Holman demonstrates that lack of love warps people just as much as lack of money.

The emotional fluidity of Bad Weather's characters, their capacity for surprising - almost shocking - changes of direction, and their literacy in discussing how they feel, makes this sincere, absorbing play as contemporary as anything by the new nihilists.

'Saturday Night Fever': Palladium, W1 (0171 494 5030). 'Cleansed': Royal Ct Downstairs, WC2 (0171 565 5000), to 30 May. 'Bad Weather': Stratford Other Place (01789 295623), in rep.