Dance Merce Cunningham Dance Company Sadler's Wells, London

Re-acquainting oneself with the Merce Cunningham Dance Company after an interval of three years is like swapping a long-term junk-food diet for a week of gourmet suppers. Cunningham is one of the established heavyweights of modern dance, but there was nothing indigestible about last week's Events and repertory programme. A Cunningham performance leaves you feeling nourished rather than sated and, more than anything else in this year's Dance Umbrella festival, Cunningham's work reverses our erosion of faith in dance. The ever-adjusting, intangible moods and intent of Cunningham's stage worlds are always underpinned and stabilised by an absolute clarity of means and purpose. That may sound paradoxical but, whether being droll, romantic or businesslike, Cunningham's performers never deviate from showing you dance at its most substantial, compelling and profound.

Ground Level Overlay, created last March, and the most recent item on the company's triple bill at Sadler's Wells, must rank as one of Cunningham's finest works. Enclosed within Stuart Dempster's Underground Overlays - a soundscape of eerie, delayed reverberations produced by 10 trombone players in a now-defunct, 2 million gallon water tank - the dancers' movement echoes the slow majesty of Dempster's music and the beautiful decay and desolation of its site of origin, as well as the instances of dire urgency contained in its measured repetitions. In the midst of racing trios and duos, Banu Ogan navigates her only path of uninterrupted, curving gestures. Like the woman who stands on one leg, swaying her lifted thigh and arm back and forth, as though waving goodbye with her whole body, Ogan registers as the calm prefiguration of some impending disaster - also heralded by Dempster's ships-in-distress horns which blast out from all around the auditorium.

CRWDSPCR leaves behind the dark portents of Ground Level Overlay for a more mechanised but equally mysterious universe. Here, the dancers travel as a group, their individual quirks detailing the mass movement but never detracting from its progress. We see the group splintering to form self- contained units, and then re-forming as though pre-programmed to do so.

Next to Ground Level Overlay and the opening piece, Beach Birds - a gentle nature study enriched by the occasional, soft piano notes and trickling stones and water of John Cage's FOUR3 - CRWDSPCR is liable to strike you as Cunningham's most unapologetic homage to computer technology. But it's no less human for the transference of software wizardry to real people. And in some of its male-female duets, in particular, the sense of deep, emotional attachment between the dancers is so unforced, credible and overwhelming that it seems to have evolved more through accident than design.