There Comes a point in an artist's life when, if they've stuck to their guns, stayed true to their muse, their work becomes unassailable. It rises above such banal considerations as to whether it's accessible or not. A quarter of a century has passed since Siobhan Davies choreographed her first dance piece and some 50 more have followed. Many people have found them difficult or obscure, but they have tended to blame themselves. "I don't understand abstract art. I don't understand the language." This month, the magazine Dance Now devoted seven articles to Davies and her work, a measure of the esteem in which she is universally held, and also of the nature of the work. Richly personal, meticulously wrought, it refuses to be pinned down. But 7,000 words get closer to naming it than one.

Each piece Davies makes is a variation on the same theme, an attempt to refine that already rarefied thing we call a personal dance language. Like any language, it has recognisable vocabulary, phrases and grammar. Unlike any language I know, it is not designed to say anything directly at all, but to clothe the human frame in layers of mystery.

This worked beautifully in last year's melancholic Affections and the fast and tactile Art of Touch. Both communicated a magnified sense of humanity that made the term "abstract" quite irrelevant. The dance spoke, that was enough. But in Brighton last week, at a performance of Davies' latest piece, Bank, (Bank of England? Bank of violets? Banked fury?), I came under the distinct impression that the fine dancers of the Siobhan Davies Company were communing with no one but themselves.

To open, there is David Buckland's set - a Japanesey parchment screen over-printed with a diagram for a piece of machinery which might have been for a patent breast pump for Mrs Heath Robinson. Someone later told me that it was a component of a plane's engine. Six dancers dressed in russet and plum dart about on stage like pawns on a chessboard, walking, running or toppling into new configurations which suggests a game with very complicated rules.

You sometimes catch the dancers cradling their own torsos, but otherwise there's little contact between them, no emotional exchange. The real passion in this piece comes from the composer-musician, Matteo Fargion, who develops a vigorous relationship with three cardboard boxes. Their strange, dry sound when slapped and tickled like an Indian tabla adds a lively texture to thin, plaintive strands of harmonica, also played by him. The only memorable bit of choreography was Gill Clarke's solo - two or three naturalistic gestures repeated like a mantra assume an almost spiritual intensity. A hand plucks a piece of precious something from the air, a palm scrutinised (for signs of guilt?) is tossed aside. Rich with secrets, Clarke's solo allows us in on a few of them. For the rest of the evening, though, I felt the choreographer had put up the shutters on her own private world.

A more playful pretext for dance was given by SOAP, who started life in an old Frankfurt soap factory and here had the honour of opening the Turning World season at The Place. We knew we were in for some hi-jinx when the show began in darkness with the company clattering to and fro filling 10 empty fish tanks with ice cubes. Left under strong lights for the duration of the show, they became a sort of equatic egg-timer. At 9.30 sharp, meltdown was complete.

The basis of Rui Horta's choreography is a kind of martial-arts workout - fierce, rigorous, and a little frightening in its armed-forces precision. But the eight characters break ranks to reveal habits and neuroses that are all too human and endearingly funny.

One girl is obsessed by packaging. Having marked out the performing space in white sticky tape, she keeps sneaking off to wrap up parts of herself, an activity her colleagues viewed with pity and horror. The sight of her joining the squad in an arm-swinging exercise while bound at the elbows had a pathos that bordered on hilarious. Another girl was obsessed with creating neat little fences around herself by rearranging the tape. Each person's odd behaviour impinges on their neighbours. A man hooked on spouting poetry inevitably got his mouth taped up - yet each was incapable of help. Their interactions triggered bursts of physical virtuosity - one man flipping another up by the heels or vaulting 10 feet over his friend's back.

It made a gripping little drama and casually brilliant dance. You could protest that Pina Bausch covered similar territory 20 years ago, but SOAP have the freshness to put their own stamp on this theatre of the absurd. When bondage-girl was snipped free of her sticky-tape, and her shirt came off, too, she became more painfully vulnerable than before. Likewise, frustrated poet paddling in icy fish- tanks. Some odd personal habits are necessary and too personal to be exposed.

Siobhan Davies Co: Sheffield Crucible (0114 276 9922), 3 & 4 June.