The Maths Tutor, Hampstead Theatre, London<br></br>A Midsummer Night's Dream, Crucible, Sheffield<br></br>Ideas Men, Barbican Pit, London

Sometimes the maths just doesn't add up

On a train bound for Sheffield last week, the guard decided to practice counting over the Tannoy, extremely slowly. "One. (Pause) Two. (Pause) Three..." We were crawling through the suburbs of Leicester, staring into our coffees, by the time the voice reached "Twenty-Si...". All I'm saying is that it was about as exciting as The Maths Tutor by Clare McIntyre. This middle-class family drama staged by Anthony Clark certainly gets his regime as artistic director of Hampstead Theatre off to a disappointing start. B-minus, must try harder, etc.

Neither the script nor the production are smart enough for this new writing theatre, which has just been ambitiously rebuilt with an expanded main house.

Firstly, the stage looks a scrappy mess with a bunch of giant picture frames hanging at different angles. These supposedly represent several socially entangled homes, for we begin at the seaside cottage of a superficially happy and nice couple called Paul and Jane, then move to their north London home, and across to that of their neighbour, Anna. She is a boozy, egocentric divorcee and her surly teenage son, JJ, is going to mean trouble for Brian, a private tutor and gay man who also teaches Paul's gentler kid, Tom. The acting feels flat, awkward and unpaced in the opening scenes, without precision directing. Sally Dexter's Anna pulls exaggerated faces attempting to enliven the answer-machine message she is leaving for her uncommunicative boyfriend. Ben McKay struggles to convey JJ's rage about his mum's affairs, kicking a football at Tom but hardly giving it any welly in case it trundles off-stage. Back at the cottage, behind Paul's superficially contented smiles, something is gnawing at the character rather too obviously and the actor Christopher Ravenscroft makes his speeches over-emphatically monotonous.

To be fair, the cast all gather emotional momentum. Some powerfully tense scenes emerge when JJ accuses Brian of molesting him, and other personal grievances and latent homophobia look set to pervert the course of justice further. Tricia Kelly's Jane, initially a soft woolly liberal, becomes especially riveting as the secretly wounded, bitter wife of a roving bisexual. Nonetheless, too often the script sounds like a TV soap with socio-political issues being ticked, box by box.

Who needs the didacticism of Anna the alcoholic single mum declaring, "You try doing it on your bloody own!", especially when Dexter incongruously delivers this line to the audience? This is, it seems, meant to be A Lesson For Us All to really Make Us Think. McIntyre, by the by, appears to have no ideas about mathematics whatsoever, except that two's company and three's a crowd in sexual relationships. Her plot doesn't quite add up either and offers low returns in the end. Bring back Septimus Hodge, the sexily brilliant maths tutor in Stoppard's Arcadia.

Meanwhile, in Sheffield, Shakespeare's partner-swapping lovers head into the forest of irrational desires in Michael Grandage's very enjoyable production of A Midsummer Night's Dream. Here Athens looks like Edwardian India, with Ray Fearon's commanding royal Theseus and Samantha Spiro's enamoured but displeased Hippolyta dressed in sombre, elegant frock coats. Out in the wilder woods, it's more tribal and carnivalesque with Fearon reincarnated as a bare-chested Oberon and with Spiro's Titania in a fiery-coloured, rag-tufted frock. The ass's mask, acquired by Lee Boardman's Bottom, is unforgettably eerie as well as comical. Essentially realistic but magically blue with devilish coal-red eyes, it has an entrancing, floating quality to it, the ears seeming to sway as if Bottom is ethereally drunk or walking under water as he dreams of being loved by the fairy queen.

Designer Christopher Oram's sweep of bare, dark wooden boards lets the poetry come across with startling clarity, as if caught in shafts of moonlight. Determining to elope with Lysander, Lisa Ellis's Hermia makes her pretty rhyming couplets sound thrillingly heartfelt and new-minted. Oberon's lyrical monologue, "I know a bank where the wild thyme blows", is invested with vengeful intent by Fearon's sinuous and razor-sharp enunciation. Emphasis is placed on passionate energy. Some charming playful comedy is simultaneously supplied by Boardman and James Tucker's Peter Quince, a scruffy, hilariously frustrated director. There are oddly tacky moments, including a snowfall of glitter. Adam Cork's lavish score and Scarlett Mackmin's choreography feel intrusive. Dylan Brown's mildly laddish Puck doesn't live up to his scarlet feathered thighs and woad-blue skin either. In fact, rather too often, the ferocity and lust only go skin-deep here. Nonetheless, well worth seeing.

Last but not least, Ideas Men made me weep with laughter. A two-man comedy about corporate losers (co-commissioned for the BITE season), it could have just aped BBC2's mock-documentary The Office. With two blokes in grey suits and one long conference table, this show also looks suspiciously like The Summit, the political satire by the experimental duo Ralf Ralf. But David Woods and John Hough, aka Ridiculusmus, are a law unto themselves and peculiarly brilliant. Their style is deliberately unpolished and puerile. They come wheeling in, sporting bad wigs, and race round and round on office chairs. Then they sit at their computer keyboards (with no screens attached) exchanging interminable inanities about their lunch-hours, prawn sandwiches and the post office. They are two sad bores attempting to "strategise a creativity role-playing seminar" without a single idea between them. They draw willies on flip-chart sheets, lamely chat up the slapper-secretary, keep running into the boss at acutely embarrassing moments, and finally go AWOL with a large hammer.

The secret is, Ridiculusmus are madly chaotic but also deft, deadpan clowns. The surreal unpredictability of these guys is a joy, suddenly putting their suits on the wrong way round, lounging with feet up on the desk but with the back of their heads where their faces should be. They also play unexpected, clever Pirandellian games with reality and role-play, for the pair switch characters at lightning speed, creating dreamlike jump-cuts. Some people might think this slight and silly - there were a few nonplussed faces the night I went. But with others the reaction was extraordinary, with spasmodic howls of laughter flaring up like will-o'-the-wisps - the woman next to me creased up silently, her head banging against the chair in front. Tops.

k.bassett@independent.co.uk

'The Maths Tutor': Hampstead, London NW3 (020 7722 9301), to 25 Oct; then The Door, Birmingham Rep (0121 236 4455), to 22 Nov; 'A Midsummer Night's Dream': Crucible, Sheffield (0114 249 6000), to 1 Nov; 'Ideas Men': Barbican Pit, London EC2 (0845 120 7527), to 25 Oct