Musashi, Barbican Theatre, London

Yukio Ninagawa’s productions are often hauntingly numinous, but what he's done with Hisashi Inoue’s play ‘Musashi’ transports us to a realm where life and death are literally one and the same.

Its jumping-off point is the duel in a medieval tale which all Japanese schoolchildren are brought up on. Two rival samurai agree to fight to the death on an island: having cannily arranged to have his back to the sun, the hero Musashi triumphs over his blinded rival Kojiro, but, since he isn’t sure whether his brave opponent is really dead, he calls for a doctor before sailing away. Kojiro survives, but now has only one ambition - to redeem his honour by killing Musashi. Inoue’s play is about what happens next.

The lights go up on a long-sword duel beneath a giant red sun: catlike, deadly, quickly over. Then the stage is invaded by a series of wooden huts and a forest of bamboo trees which are in constant movement, while a tango gently plays. Finally everything comes to rest, and we’re looking at a bosky temple designed like an open-air Noh theatre. Traditional Japanese music - a shakuhachi, a woodblock, Noh chanting - combines with a Western cello and organ to create a pleasantly disorienting effect. Years pass, the rivals re-meet, but decide to rest before their fight: most of the play concerns attempts by the peaceful denizens of the temple to dissuade them from trying to kill each other.

The tenor of the debate is down-home village stuff, with Ninagawa’s ensemble achieving marvellously deft feats of choreographed comedy. Samurai heroics are grotesquely defused by turning them too into a tango, but under the shock of sudden violence - an arm (very realistically) cut off - the debate turns into a passionate discussion about cycles of revenge. Then extraordinary things begin to happen, which a responsible critic should not reveal. Suffice it to say that nobody is what they seem, and that the samurai are as much in the dark as we are, until the astonishing denouement with its message about the preciousness of life. Never has this great director created such a serenely terrifying, Prospero-style spell, where lighting, music, and spectacle conspire first to frighten, then to steer us into a profoundly philosophical calm.