Merce Cunningham, Tate Modern, London<br></br>Planted Seeds, The Place, London

Eighty-four-year-old alien takes over the south bank

Close encounters of the third kind don't come closer or more spine-tingling than the one that occurred at Tate Modern last week. Ostensibly the event celebrated the Merce Cunningham company's half-century birthday and the climax of Dance Umbrella's 25th. In effect, though, it was Close Encounters on Bankside.

Even before the show began, there were echoes of the famous film. Onlookers in the Turbine Hall, blinking in the misty solar glare of Olafur Eliasson's Weather Project installation, stretched out on their backs on the lobby's great slope as if bedding down for the week. Others milled about the perimeter of three landing pads as guards with walkie-talkies gruffly kept them clear. Fog swirled, yawning violin and piano sounds echoed. By the time Cunningham's dancers emerged on the floor you were ready to believe in spaceships.

And there is a touch of the extra-terrestrial about Cunningham's dance, composed as it is by means of chance processes that banish cliché - the movements body parts might naturally fall into if left to mere human imagining. A Cunningham event is doubly unpredictable in that it's a one-off patchwork of old and new material adapted to a particular space. Straightforward enough, you might think, but for the extraordinary fact that until the eleventh hour the dancers do not know which sequences will be danced, nor the music that will accompany them. Order and casting are decided by the flip of a coin just before each event begins. "It makes it more fun," Cunningham has said.

More fun for us, too. Viewed close (literally under your nose, if you wangled a good standing place), you could spot secret smiles being exchanged whenever music and motion accidentally mesh for a few seconds. More often, though, they are cheerfully at odds: great somnolent washes of electronic noise (from Takehisa Kosugi, perched up on the Turbine Hall bridge) accompany a girl fast-hopping like a crazed elf; harsh scrapings assault a lush, fondant arabesque from a girl with the calm of a sphinx. Some statements are grand, virtuosic. At other times miniscule shifts of body weight carry the drama. The elements may be dispassionately random, yet the compound effect is always human, often intensely so.

Faced with a choice of three performances at once, it was hard to know whether to stick with one, or roam about and nibble from each, adding yet another layer of serendipity. A third way was to gaze up at the mirrored ceiling where the three sets of colour-matched bodies (lime green, white, cerise) became the beads of a kids' kaleidoscope, forming Miro-like constellations. A further attractive option was to line the narrow runway that joined the three spaces and feel the rush of air as dancers sprinted like Ancient Greek messengers to their next assignment.

And all this from the brain of an 84-year-old showing no sign of closing the book. His own body may be halt and lame (arthritis now forbids the curtain-call cameos he delighted fans with until a few years ago), but the mind gallops on. No doubt this particular event gained immeasurably from its unique setting (who was the genius who saw that dance could co-exist with orange fog?), but no Cunningham experience I have had left me so bereft when it was over.

Drama of a different tenor had The Place in its grip, as Darshan Singh Bhuller revived his harrowing 1998 dance-theatre piece about the Bosnian conflict. Planted Seeds was inspired by accounts of the atrocities Bhuller heard from young Serbs and Muslims he met in Sarajevo, and at its first showing five years ago it gave the provincial dance-tour circuit a nasty shock. Taking up where TV news left off, the piece dared set foot where dance has rarely gone before, persuading a complacent audience to engage with ugly, recent, historical fact.

Bhuller has re-set the piece on Phoenix, the company he now directs, and though it has inevitably lost with the passage of time some of its foreign-news-page clout, it has gained a more generalised relevance to other trouble spots in the world - most of them, when you think about it.

Powered by a range of stirring music from Gorecki to Balkan disco, the first half centres on the plight of the women (20,000 at one count) who endured systematic rape by the Serbs, the rest on the story of Sarajevo's "Romeo and Juliet" who were gunned down for their frowned-on liaison. It sounds grim, and there are times when you could scream for the sheer intractability of the facts, the wretched casualness of the rape acts, the grubbiness of pot-bellied dance-actor Bob Smith's vest. Yet Bhuller's approach is sufficiently oblique and inventive as to make what you feel about the violence greater than what he actually shows (otherwise, frankly, we couldn't sit through it). None of it makes easy watching: one of the most striking motifs from the women is a kind of emergency bracing position as recommended on airlines. Race hatred? Self-loathing? Bhuller gets closer to a physical embodiment of these abstract horrors than I imagined possible. He also knows how to add balance in passages of pure, uplifting partying. In even the darkest corner there is light.

jenny.gilbert@independent.co.uk

'Planted Seeds': Patrick Centre, Birmingham (0121 689 3040), Wed & Thur; Farnham Maltings (01252 726234), 20 Nov; The Lowry, Salford (0870 787 5790), 26 & 27 Nov