The Forbidden Zone, Barbican, London — ‘Stunning, sombre’

Well, this is Katie Mitchell at her very best. In this stunning, sombre piece of theatre, the director works with her regular collaborators 59 Productions, interlacing theatre and live video to tell the neglected story of Clara Immerwahr and her granddaughter: two unsung casualties of chemical warfare.

Immerwahr was a chemist married to Fritz Haber, the German scientist who worked on the creation of chlorine gas in the first world war. She committed suicide, shooting herself on the night Haber hosted a party to celebrate the deployment of the gas at Ypres. Three decades later, her granddaughter Claire Haber (hauntingly played by Jenny König), who was working in Chicago on an antidote to the chemical weapon phosgene, would also take her own life, apparently in despair at the fact that her work had been halted (the focus was shifting to atomic weapons).

The piece (produced by the Berlin Schaubühne, performed in English and German with surtitles) explores these two stories in short episodes, switching back and forth and linking them further by including a nurse whose sweetheart was gassed at Ypres. Duncan Macmillan’s script skilfully uses words by writers such as Mary Borden, Virginia Woolf and Simone de Beauvoir to voice the thoughts of these women and the powerlessness they feel in the face of war.

It is desolate and brilliantly executed. A life-sized train carriage dominates the stage, with other locations — a garden, a laboratory, a public toilet — all just visible in the recesses behind. As the cast act out the scenes we peer into the train and the various rooms, piecing together their stories, while above the stage their actions are relayed live on a screen, looking every bit like a period film. The double perspective — the fact that we can see camera operators running about and observe how tricks are done even as we watch the results — doesn’t detract from the intensity: if anything, it increases it. There’s a calmness and solicitude about it, and a forensic quality that seems to honour the women.

Even when we see Ruth Marie Kröger, playing Clara, shift so that she can tumble on to to something soft, it takes nothing away from the moment she fires the gun — in fact it emphasises the effort it takes to make that protest. As the train rattles on, empty, at the end, it is clear this is as much about the present as the past: an overwhelming piece about the hideousness of war.

To May 29, barbican.org.uk