This horrifying piece of documentary theatre tells us nothing new about the hellish atrocities of Auschwitz or the brisk efficiency with which thousands of men, women and children were daily gassed and burned to ashes. Yet as conceived by Dorcy Rugamba and Isabelle Gyselinx, who also directs, Jean Beaudrillard's adaptation of Peter Weiss's play The Investigation achieves a chilling, contemporary resonance that is all its own.

For Rugamba was prompted to create this production by direct experience of a more recent genocide. Twelve members of his close family were murdered in the first months of massacres in Rwanda during 1994, when half a million Tutsis and more moderate Hutus were shot or hacked to death. Most of his actors come from Rwanda, too.

Rugumba's decision to stage The Investigation, therefore, poses nagging questions. How did the Rwandan Genocide come about, a mere half century after Hitler's incineration of six million Jews? Why did the world react with such indifference?

At the end of this version of The Investigation, which condenses the five-hour text to 80 minutes, a depressing conclusion is reached. "The society that produced the (Nazi Extermination) camps is our society." Countries, creeds and cultures may be natural-born generators of genocidal impulses.

On a platform stage, actors who speak in French (with English surtitles) group and regroup in elegantly choreographed patterns. Interchangeably they speak the testimonies of Auschwitz medical/administrative defendants or executioners who stonewall or sometimes furiously challenge the charges of their survivor/victims.

The actors who play the survivors in Rugumba and Gyselinx's graceful production adopt an almost uniformly detached, emotionally restrained tone that renders their recollection of Auschwitz all the more terrible. Each process, from arrival in cattle-trucks to gassing or excruciating, slow death from disease and medical experimentation, is duly described.

Corpses tumble from cattle trucks. The living are assailed by sickly sweet odours of burning flesh before many are sent straight to be gassed. Rats gnaw the feet of the dying. Diseases known only to textbooks spring back to deathly existence. Excruciating tortures and medical experiments are devised.

By bearing renewed witness to Auschwitz's depravities, as if to provide the amoral context for Rwanda's butcheries, this amazing company of Rwandans encourages us to brood about our moral lethargy in face of resurgent genocidal tendencies. A gruelling but unforgettable experience.

• Until 10 November (020 7922 2922).