A Matter of Life and Death, NT Olivier, LondonVernon God Little, Young Vic, LondonElling, Bush Theatre, LondonThe Letter, Wyndham's Theatre, London

A flock of nurses, all in white, are pedalling upside down, lying on their backs with bicycles between their legs. One hospital bed has, surreally, burst into flames. A huge moon is spinning, up above, and a mental patient launches into an aggressive rap song.

Anyone who hasn't seen Powell and Pressburger's classic Second World War movie might, briefly, wonder what on earth is happening in the NT's new stage version of A Matter of Life and Death. Cinephiles unfamiliar with the freewheeling imagination of Emma Rice - director of the exhilarating physical troupe, Kneehigh - may be in free fall for a moment too. But after a second it's clear. This is a bombing raid and Squadron Leader Peter Carter's strafed plane is going into a nosedive. Tristan Sturrock's Peter has feverishly fallen in love with Lyndsey Marshal's June, the radio operator trying to save his life. He then bails out with no parachute. Leaping from his cockpit - the top rung of an arcing ladder - he hangs from two thin wires in space, slowly somersaulting, head over heels.

When he wakes up on the seashore, he may have tumbled into the afterlife, be hallucinating or have miraculously survived. He joyfully finds June, wheeling past on her bike, before his brain damage becomes apparent and he has visions of having to face trial in the beyond, for giving death the slip.

Rice's work has reached a new level of technical wizardry here in the Olivier, but without losing her playful inventiveness. Blips and slack patches do arise, including a tediously expanded role for Kneehigh's founder-actor Mike Shepherd. Gisli Orn Gardarsson's quirky clowning becomes slightly tiresome too, playing the spirit-catcher, Conductor 71 as a flailing illusionist-contortionist. However, Marshal and Sturrock are poignantly intense and ecstatically loving, undressing and falling into each others arms as if they are flying, spun over the shoulders of the supporting cast on to a bed that swings like a giant pendulum against an sudden explosion of red flowers.

Rice and her team's vision is entrancing, with much of the original dialogue interwoven with aerial gymnastics and filmic projections - which never slavishly borrow from the movie. Composer Stu Barker's on-stage band makes this an alternative musical as well, with sultry tangos and eerie campanology.

In Rufus Norris's staging of DBC Pierre's adapted Booker-winning novel, Vernon God Little, the titular adolescent goes on the run after his best friend guns down their smalltown Texan classmates. Vernon stands accused of being a fellow psycho. Ultimately, Colin Morgan's Vernon is framed, found guilty and lethally injected.

The deliberately dirt-poor aesthetic of Ian MacNeil's set reflects the run-down morals of Pierre's white-trash characters. It is also humorously imaginative, with old sofas on wheels morphing into a dance of cars on a highway. This is another wacky musical too, with line dancing and country songs. Mark Lockyer is scene-stealing as the dodgy newsman, Lally, and the gangly, loping Morgan is impressively confident for a newcomer. That said, Vernon is less obviously sympathetic in the book. Other characters look like crude cartoons when fleshed out and, though Pierre's plot gains welcome momentum, the bleak conclusion feels immature.

Elling is another comedy about psychiatric cases, adapted by Simon Bent (from a Norwegian dramatisation of a novel by Ingvar Ambjornsen).

Small, pallid John Simm (from Life on Mars) and tall, dark Adrian Bower (from Teachers) play cranky buddies let out of the loony bin. Bower's Kjell is an excitable simpleton, obsessively keen to get laid by a lady, and Simm's Elling is a paranoid ex-mummy's boy. Eventually, each sociably finds another soul mate, getting over jealous fits.

This show has landed some rave reviews but you'd have to be nuts to think it a seriously good play. It is calculatedly The Odd Couple crossed with One Flew Over the Cuckoo's Nest. The protagonists are essentially two-dimensional clowns and Bent had left many lines sounding like a literal translation.

Nonetheless, Paul Miller's production exerts an irresistible charm. The dialogue is scattered with explosively funny, off-kilter comments. ("Mother did all the shopping. I was in charge of ideology.") Bower is distractingly gorgeous: some sort of compensation for never being convincingly backward. Frankly, most ladies in the audience were gawping more than he was. Meanwhile, Simm owes an awful lot to Rowan Atkinson but he is hilariously uptight in his buttoned-to-the-neck raincoat, with ramrod arms, snapping like a Pekinese with the occasional sly pause.

Lastly, Somerset Maugham's The Letter ought to be cryingly funny. This colonial 1920s murder-mystery is nearly that bad, with Jenny Seagrove doing a superlatively wooden impression of a dry stick as Leslie, a pukka plantation-owner's wife who has shot a chap in self-defence - or was it a crime passionel? Anthony Andrews, playing her lawyer, demonstrates that he smells a rat by directing endless stares into the middle-distance - or had he spotted another criminally bad actor in row M?

To give him credit, Alan Strachan's production brings out the ex-pats' vile racism and that the lawyer may also be hiding in the closet, being a jolly close chum of Leslie's husband. Really though, darlings, the acting is just too frightful.

k.bassett@independent.co.uk

'A Matter of Life and Death' (020 7452 3000) to 21 Jun; 'Vernon God Little' (020 7922 6363) to 9 Jun; 'Elling' (020 7610 4224) to 26 May; 'The Letter' (0870 950 0925) to 11 Aug