Tejas Verdes, Gate Theatre, London

When Colorina was a girl, her favourite bedtime story was Hansel and Gretel; she used to cry when the birds ate the breadcrumbs and the children couldn't find their way back to their parents' house.

When Colorina was a girl, her favourite bedtime story was Hansel and Gretel; she used to cry when the birds ate the breadcrumbs and the children couldn't find their way back to their parents' house. Little did she know that the fate of those fairy-tale characters would become symbolic of the story of her own generation in Chile after the 1973 military coup by General Pinochet.

Colorina was one of the "disappeared". Through artfully interconnected monologues, the circumstances of her tragic end are pieced together by the various speakers in Fermin Cabal's deeply distressing Tejas Verdes ("Green Gables"). The play takes its name from the converted seaside hotel that became the army's infamous detention and torture centre. It was here that the interrogators tried to extract from Colorina the whereabouts of her Marxist boyfriend.

Thea Sharrock's British premiere of the piece is almost suffocatingly powerful. For her promenade staging, the Gate has been converted into a dark, eerie forest of remembrance and forgetting. Issued with a torch, you stumble down to this hot space past stacks of files and a wall of memorials. Assigned the role of impotent bystanders, you find it hard to meet the gaze of the speakers who push into the crowd. The excellent cast is all-female, for the play heightens our sense of the polluted politics of the regime by emphasising that men did not have a monopoly on viciousness.

For example, the military doctor who outrageously claims that the allegations of torture are just the fantasies of female hysterics (masking "hidden desire") is a woman. So is the lawyer on Pinochet's defence team who castigates liberals for not seeing that the leader was a "stabilising" influence.

It was not a good time to be a gravedigger. To help the relatives of the disappeared was to risk being buried alive as a punishment. As she frantically struggles to unearth her husband before he expires, one woman pictures what she is doing as a travesty of childbirth and as emblematic of why you would not want to bring a baby into this world of death.

People were reduced to becoming collaborators in conditions of appalling cruelty. The woman who informed on Colorina talked in order to stop the torture of her six-year-old son, whose fingers were being broken by nutcrackers. The one freedom you are left with is the capacity to forgive, as Colorina does this informer when they end up in the same prison: "in spite of the blindfolds we always wore, I know she meant it. The hands never lie".

Colorina could eventually have walked free, if she had not fatally insisted on a medical report confirming her injuries. In the mystical concluding section of the play, her spirit looks forward to the Last Judgement. Meanwhile, we can take some comfort from the fact that in 2004 Pinochet was stripped of his immunity from prosecution.

To 5 February (020-7229 0706)