Every so often theatre is capable of lobotomising that part of the brain that constantly reminds itself of the artifice of drama. And when that happens it can leave a viewer so utterly exposed to the rawness of a moment, a kind of post dramatic stress descends in the aftermath.

It happens in Robert Icke's very free and modern adaptation of Aeschylus's Oresteia plays - the opening of the venue's Greek season - as the rangy Angus Wright's thoughtful and emotionally aloof Agamemnon sacrifices his daughter for the purpose of winning a war. If the scene had taken place on an altar - as reported in Euripides's version of the story - it would have been potent enough. But Icke sets Aeschylus's version in the 21st century domestic minimalism of Agamemnon and Klytemnestra's family home. Iphigenia here is not much older than a toddler and the agonisingly convincing sacrifice is administered "humanely" with pills. It's the bloodless, procedural quality of the deed that makes it so believable; the deliberate banality that is so harrowing.

Yet this is also a thrilling three and a quarter hours. Yes, it is a daunting amount of time to sit in the theatre (there are regular breaks). But the epic themes of Greek tragedy - the cyclical nature of bloodletting, the condition of being notionally free but under the control of a greater, perhaps higher force - are all played out here on a domestic scale. So immediate are the events as they unfold, it is as if our noses were pressed to one of the house's sleek, sliding glass doors, behind which sits the bathroom that waits for death like an altar.

The cast - epitomised by the terrific Lia Williams as a cool but never remote Klytemnestra - get the pitch just about right. That control is mirrored by the dramatic thrust of the show, which, in a revelatory twist, reveals the underlying psycho-drama of the work. Events here unspool in the mind of Orestes. And they will echo for a long time to come in the mind of those who watch them. I left in a daze.