The lift Festival, now in its ninth year, has scoured the world for shows which stretch the boundaries of what we understand as theatre. This season's find from Argentina, a company called De La Guarda, goes beyond what most people have seen even on the fringes of theatre, dance, and circus. Back in Buenos Aires, the company has a reputation for kissing its audiences and drenching them in water. I'd call it sensory assault. There's no law against it for consenting ticket-buyers.

Here's what happens. You are herded into a small marquee made of paper and left in darkness to negotiate your square foot of elbow-room. Spidery shadows and scuttlings are dimly perceived above. Coloured beams flicker and flow. Watery electronic sound encourages the sense that the spectators are at the bottom of the sea, or perhaps peering up at a canopy of rainforest. Tiny beads spatter down onto the drum-like surface above their heads and disperse like bubbles. Gobbets of oil form luminous spheres that merge and divide like amoebas on a biologist's slide. It's all rather benign and beautiful, a kind of magic-lantern show on the ceiling.

But not for long. The light shower of small objects becomes a downpour - balloons, plastic toys, billions of bus tickets. A hand-held storm lamp burns a hole through the paper roof and all hell is let loose: wriggling arms or legs appear through holes like some medieval depiction of torment. Entire bodies burst through and bungee up again, sometimes snatching up a member of the crowd as they go. The roof and walls are ripped open, our "theatre" is destroyed, screwed up and discarded like chip wrappings.

Unveiled, the perpetrators of this scene look shockingly ordinary: eight young people dressed for a day at the office. The boys have to hitch up their jacket sleeves, the girls their tight skirts, as they scale the walls like monkeys, swing on ropes to within an inch of collision, and fly off scaffold towers ululating like demented Tarzans. Two girls perform an astonishing abseiling duet, ants scuttling over a vertical wall at a speed that makes you blink. Under strobe lights, they became flicker-book Lois Lanes, making nonsense of a skyscraper with their sucker- pad feet.

The dousing comes next, delivered by spray hose as if routinely controlling a fire. We've all heard of shows where the crowd gets a bit of a wetting. Not like this one. The only comfort is seeing that the performers come off worse. Plastered hair and sodden two-piece suits add even more desperate glamour to their antics, along with bared teeth and utterances that I imagine translate from the Spanish as "look out I'm coming" and "aaaaaargh". At one point all eight performers lash themselves precariously to one

rope-end and swing violently to and fro, limbs flailing, seams straining, clutching at some imaginary life-buoy that remains for ever out of reach. It's the office party on The Raft of the Medusa.

It's tempting to search for political meaning in this physical mayhem, but I suspect the appeal is entirely to the senses. In any case, the action moves so fast there isn't time to think. Aerial Lotharios swoop into the throng to beg full-lipped kisses from unwitting men as well as women. The girls throw themselves into the arms of strangers and try to get them to dance. Didn't anyone tell these Latins that the British would sooner pay twice than let go their inhibitions? A pity, for the live music is thumpingly good, latching on to the theme of exhilaration through muscular effort: thwacking a drum, yodelling at full throttle, or blowing long, strong chords on plastic bugles.

The standard British advice for an assault course like this is to take a mac. Perhaps we should take all our clothes off instead.

Three Mills Island Studios, E3 (0171 312 1995), to Sat.