Bent, Trafalgar Studios London <BR/> Metamorphosis, Lyric Hammersmith London <BR/> Longwave, New Greenham Arts, Newbury

Two winters ago, Daniel Kramer directed an unforgettable Woyzeck at Notting Hill's tiny Gate Theatre - with thuggish army violence unnervingly danced out like rock 'n' roll. That production deservedly transfers to New York next month. In the mean time, Kramer's new production of Martin Sherman's famed 1979 tragedy, Bent, has opened in the West End. Alan Cumming stars as Max, the goodtime gay in 1930s Berlin who, after the Night of the Long Knives, finds himself being hunted down by homophobic Nazis then imprisoned in a concentration camp alongside Jews and other so-called degenerates.

It must be said, if you wish for truly great writing, this play has not fully stood the test of time. Sometimes it's rushed, sometimes repetitive, sometimes too calculatedly tear-jerking. Kramer's directing is rough around the edges as well, exposed on a large, scrappy stage. The opening scene with Max tottering around his apartment in a kimono - so hung over he's forgotten about his boho night-before - is clearly meant to be a little domestic farce, sown with the seeds of trouble. Max's lover, Rudy, sashays around like a camp housewife in pink satin, then a kinky, hunky Aryan pops out of the bedroom, sporting only Stormtrooper boots and parading his wares. Unfortunately, the singsong prattle of Kevin Trainor's Rudy, with insufficient comic timing, is tiresome. And if he and Cumming are supposed to be self-consciously acting like a cabaret duo, Kramer leaves that half-baked. More problematically, when the persecution gets serious, the leering Gestapo keep looking like crude caricatures.

That said, Cumming becomes increasingly moving and harrowed as the play gets stronger and confronts Max with devastating moral crises - particularly when his terror and survival instincts drive him to violence in obedience of SS orders. There are also moments of fragile but triumphant humanity, when Max and his Dachau friend, Horst (outstanding newcomer Chris New), keep each other alive by just imagining and talking about holding each other. The play's worries about Max's sadistic streak and fear of tenderness - which Horst condemns as akin to the Nazis - strikes me as bravely polemical. However, some might critically lament the closing image of him, finally casting aside his cadged yellow star for a frank pink triangle, standing up to be counted only to kill himself.

Gregor Samsa is in a prison of his own sort - in a far more surreal but also implicitly fascistic realm - in David Farr's new staging of Metamorphosis (with lyrically melancholic background music supplied by Nick Cave and Warren Ellis). Freely co-adapted and directed by Gisli Orn Gardarsson of the Icelandic troupe Vesturport, this is an acrobatic and visually startling reworking of Kafka's nightmare about the young drudge who wakes one morning to find he has turned into a beetle.

There are blessedly no cockroach costumes here. Gardarsson plays Gregor in a disheveled grey suit and tie but he is physically, literally going up the wall. Above the Samsas' dour dining room, their son's shadowy bedroom has actually flipped 90 degrees, courtesy of Borkur Jonsson's dizzying set design. Gregor's standard lamp and potted palm are sprouting out of the wall, and we seem to be gazing down at this poor crazed creature from a high corner as he stares out, bug-eyed, from his vertical bed. Rigid and hanging out from the mattress (with straps round his wrists), he looks as if his whole being is in the grip of hair-raising terror. To the horror of his family, he then comes sliding down the banisters, like a hunched spider interbred with a monkey. He scurries across the ceiling (using hidden handles) and dangles over his seething father's head. When he speaks, we can understand him but his neurotic, spindly mother (Kelly Hunter) clasps her hands over his ears as if he's making an intolerable din.

Gardarsson isn't an absolutely first-rate actor and he is, now and then, allowed to rely on one expressionistic posture for too long. The gymnastic skills can also be obtrusive (not least trampolining). But Gardarsson's performance is surely vying with Antony Sher's legendary arachnid Richard III, and his Icelandic accent actually helps convey Gregor's alienation.

The allegory, informed by Kafka's own life, is at once clear and complex, implicitly depicting a stigmatised invalid and cruel carers, but also an artistic type stuck in an oppressive society and going wild - finding some liberation in running mad as well as terminal lonely despair. By updating the story to the 1930s, Farr also makes Kafka apparently foresee the rise of Germanic Nazism. Gregor's sister swiftly begins to resemble a member of the Jungmadel, if not a brutal contemporary prison guard, while his uniformed father ominously starts shouting that work will set everyone free.

In Longwave, directed and co-devised by the sensitive experimentalist Chris Goode, two geeky scientists are holed up in a wooden shed in what might be the Antarctic. Barely a word is spoken and that is a limitation at points, with slightly too much whimsical kidult clowning. But you can't help giggling at the batty DIY lab tests that Tom Lyall's Max and Jamie Wood's Herman conduct, obsessively subjecting what looks like a mini-haggis to hyperdermic injections and psychological trials with Rorschach inkblots. Moreover, using only music and overlaid distant voices coming through a crackling radio, Longwave gently grows into a study of flatmates, of fetishistic nostalgia, loneliness and unspoken love.

While Gardarsson's Gregor vanishes into a deep well of gloom when he finally opens his window and lets in the wind and rain, by contrast Herman ultimately works up the courage to follow Max into the wilderness, stepping out of the door in a blaze of white light that just might be full of new hope and adventure. A haunting image.

k.bassett@independent.co.uk

* 'Bent' (0870 060 6632) to 13 Jan; 'Metamorphosis' (0870 050 0511) to 28 Oct; 'Longwave' on tour at Chipping Norton Theatre (01608 642350) 12 to 20 Oct