Bam! To deafening rock, a sequinned Elvis-figure hip-swivels in strobe lights until, with the music still pounding, the stage goes black. Then - sudden silence, bright light, and two spivs in sharp suits perched on stools. A coup de theatre, carried out with whip-cracking precision. OK, Jez, you've made your entrance, now what about the play?
The spivs begin to talk. Very fast, through clenched teeth, in a curious home-made rhyming slang, late Eighties grafted onto late Fifties, Stepney on the make in Soho. The quick-fire patter throws out jokes like confetti, but they're only half-formed - no time to linger. Whether I'm laughing at the lines, or the manner in which they are delivered, I'm not sure - I'm bemused. No matter: since this theatre's admirable programme includes the script of the play, rather than the usual West End guff, one can always check later.
The scene is a Dean Street nightclub, and there's a spot of bother. Something has happened to the owner, and a rival gang is moving in on the turf. The owner's son and the small-time hoods who run the joint aren't sure what's happened, or what to do. When the owner makes his entrance in two separate dustbins, violence breaks out all over.
Welcome to the authentic world of the Krays, though convulsively foul- mouthed in the manner of their present-day successors. And of Reservoir Dogs, with which Butterworth's play has a lot in common, from the spivvy suits to the cleverly-choreographed business with guns and knives. But while one senses Tarantino grinning like a cruel child at the fantasies he's un- leashed, Butterworth seems genuinely curious about the druggy characters he has created.
Apart from the Elvis figure - whose main job is to hang upside down and get kicked from time to time - all the parts in this play are rich with interest and, under Ian Rickson's direction, acted with superb accomplishment. In the central role as the owner's baby-faced son, Tom Hollander brings out his character's strange mix: one minute discoursing on the beauties of the countryside, the next minute shooting a man who irritates him. This pint-sized virtuoso has an absolutely Protean talent: he was the winsome Celia in Cheek by Jowl's all-male As You Like It, and the satanic Macheath in the Donmar Threepenny Opera. His performance here suggests the compulsive sadism of a once battered child. Mojo isn't perfect, but it's a nudgingly clever piece, and by a mile the sharpest show in town. But it's still a romp for the boys. Can Butterworth create a female character? We wait with interest.
Harder questions are raised by Michael Frayn's new comedy at the Hampstead Theatre. Now You Know takes place in the offices of an open-government pressure group, headed by one of those mavericks such organisations throw up, a congenital but charismatic misfit played by Adam Faith. Frayn has successfully visited office-territory before - with Alphabetical Order, which opened in this same theatre exactly 20 years ago - and he confidently delineates a world of cosiness and claustrophobia, where raiding a pack of biscuits or misplacing a wire coat-hanger become capital offences.
Things are galvanised by the arrival of a beautiful young civil-service defector, armed with a secret report. The report is political dynamite; in her effect on the office, the woman (played by the statuesque Louise Lombard) is a human time-bomb. By the end of the first act, Frayn has wound up his characters like a watchmaker, and mined their paths with devilish care.
Then he blows it. The second act is clumsy, shapeless, and goes off at odd tangents, as though Frayn is desperately evading the consequences of the conflicts he's set up. Every so often the action is held up by a consciously literary tirade, betraying the play's parallel existence as a novel. At the climax, the central character transmogrifies into someone else, turning on his staff - black, handicapped, or girly female, every one a crude stereotype - with sudden and incom- prehensible venom. Done without a trace of distancing irony, this is embarrassing to watch.
The rumpled Faith makes an improbable lady-killer, and - is it him, or is it the writing? - there's something wonky and shifting about his tone. There are no weak links among the rest of the cast who, under Michael Blakemore's choreographic direction, attack their roles with comic zest. The heroine of the evening is Rosalind Ayres, playing the office harridan (and devoted slave) we've all met at some time or other, though never with such vivid poignancy.
The play's message about openness is banal, and it ends in a tangle of questions which a dramatist of Frayn's experience should have felt duty-bound to resolve. Why have things gone so wrong? Why didn't Blakemore - director of many Frayn plays, including his masterpiece, Noises Off - take matters in hand? We all want to see Frayn find his form once more. He had the humility to go on rewriting Noises Off many months into its West End run, until he finally got it right. With Now You Know - or rather, don't know - he has a bigger task. But there is a decent play here, struggling to get out.
Richard Harris's Dead Guilty starring Jenny Seagrove and Hayley Mills is the fruit of just such a process, having undergone drastic surgery and a name-change since its out-of-town birth two years ago. Seagrove plays the traumatised and house-bound survivor of a fatal car accident; Mills is the victim's fluttery widow who comes to visit. Spooky things happen, with echoes of Gaslight and Death Trap.
With this sort of play you feel challenged to write the second act in the interval: I wrote it, correctly, half way through the first. In a good thriller, audience and victim make their discoveries in tandem; there aren't enough twists in this plot. But under Auriol Smith's direction, this excellent cast (Niall Refoy outstanding as Seagrove's goofy helper) provides two engaging hours.
With this week's fourth new play - who said the theatre was on the rocks? - Jonathan Harvey looks set to repeat the success of his coming-out romance Beautiful Thing, which also premiered in the Shoebox at the Bush. Boom Bang-A-Bang, set in a Kentish Town flat, starts as a Eurovision Song Contest party and ends as something darker and more serious.
A copy of My Night With Reg sits among the gay-sex magazines on the coffee table and echoes of that grave comedy permeate the evening. The television's auto-destruction triggers a series of explosions which director Kathy Burke handles with consummate skill as secret loves and buried neurosis threaten to blow the place apart. The superb cast do full justice to their marvellously observed parts. Harvey's portrait of a gay subculture is abrasive, hilarious and tender; the ideal complement, in fact, to the ultra-butch Mojo.
'Mojo': Royal Court, SW1 (0171 730 1745), to 12 Aug. 'Now You Know': Hampstead, NW3 (0171 722 9301). 'Dead Guilty': Apollo, W1(0171 494 5070). 'Boom Bang-a-Bang': Bush, W6 (0181 743 3388), to 19 Aug.