Scan/Rosemary Butcher Company, Hayward Gallery, London

Through the magnifying glass

Rosemary Butcher is too quietly perfect to make a major splash or attract mass audiences, but for 25 years she has been making pieces of rare distinction and distinctiveness. She has pioneered a genre in which dance, fused with the work of visual artists and composers, seems a living, breathing form of installation art. To underline that dimension, she often shows her work in non-theatrical spaces, such as the Hayward Gallery for the London premiere of Scan, in which the audience sat close round the sides of a small square stage. Scan, made in 1999, lasts 40 minutes and, like all great performances, it seemed even briefer.

Butcher's reputation in the dance world is such that she attracts the best dancers ­ such as Lauren Potter and Henry Montes, Paul Clayden and Rahel Vonmoos, who make up Scan's quartet. They are at the peak of their craft, neither too old nor too young, but mature enough to bring with them an interesting, lived-in depth. They start in a tight clump, their phrases of contrapuntal movement jagged and jostling. Soon they form partner-swopping couples who engage in furiously intense games of leverage, support and restraint. There is no unison, yet it's obvious that each couple echoes the other and derives their dance from identical images, differently expressed. Is the seating too near for a proper view of the overall patterning? But that way you feel the dancers' physicality as they pant and their skins grow damp with effort and they lunge out towards you, so close you could grab an arm.

Cathy Lane's soundtrack might be amplified breathing, and gradually you realise it is, as it quickens and becomes layered with fragmented words. The lighting design by the artist Vong Phaophanit creates a crepuscular environment, modulated by changing stripes of light that divide the floor ­ until these are replaced by close-ups of dancers' hands and feet on film projected from above. At this point, the performance shifts: the dancers leave; the camera angles draw back to show whole bodies moving in a dance studio; and the sound similarly opens out, to become clearly identifiable as the gasping and thudding of dancers and the voice of Butcher, giving instructions.

So Scan is like a detective novel, its clues progressively building a picture of the dancing body, its muscles and its noises. And eventually you also understand that the piece has travelled in reverse, from being the finished performance of itself, to its genesis in the studio. Just like a hospital scanner will show you the body from the outside to the inside, so Scan is an accomplished journey from external product to internal process, and another pinnacle on the graph of Butcher's successes.