Under the Curse, The Gate, London

The girl just can't help it

Iphigenia was the daughter sacrificed by Agamemnon to Artemis in order to secure a fair wind for his warships on their way to Troy. But a less cruel variant on the myth has the goddess whisking the girl off the altar at the last minute and whirling her through the air to Tauris, where she becomes Artemis's votary among the barbarians. When this play opens, Iphigenia, girl no longer, has been moping in Tauris for over 10 years, holding the rough and ready King Thoas at bay and persuading him not to sacrifice all strangers to the goddess, as has been his custom. The Trojan war is over, and Iphigenia knows nothing of its terrible aftermath: that her mother Klytemnestra and her mother's lover killed her father on his return, and that her brother, Orestes, killed Klytemnestra in revenge. In one of those "bad day" scenarios so beloved of Greek drama, King Thoas loses his patience with his reluctant priestess and insists that the next strangers to appear must be slaughtered on the temple steps, and guess who the very next visitors turn out to be? Why, the fugitive Orestes, pursued by his Furies, and his faithful cousin Pylades!

Euripides' original play, Iphigenia in Tauris, was reworked by Goethe as Under the Curse, and the enlightenment version is the one presented in the Gate's ambitious season of updated Greek myths. The action takes place in this middle realm between the world of the gods (a minimalist blue rectangle up in the lights) and the underworld (a sinister grating into a void where a red light intermittently glows). Direct intervention by Artemis notwithstanding, none of the characters seems too clear on the distinction between the gods' wishes, their own desires, and the voice of duty. Their sensibility is almost modern, therefore, and there's more than a touch of the Rights of Woman in Iphigenia's indignant speeches to Thoas, who, when spurned as a lover, is ready to sneer at feminine wiles. In the original play, I'd imagine it's Iphigenia's virgin status and her aura of enthusiasm (in its original sense of en theos, the god within) that makes her untouchable. With the enlightenment gloss, she's endowed by Goethe (and by Dan Farrelly in this crisp, fast-moving translation) with the irresistible power of reason. With this tool, she will also cut through the coils of the infamous curse of the house of Atreus, caused initially by too much familiarity with the gods.

Catherine McCormack's willow-slim Iphigenia quivers with unbending righteousness, which perhaps accounts for her peculiar from-the-collar-bones-upwards style of acting. This physical stiffness contrasts intriguingly with her voice, with its post-Romantic artlessness and stammering authenticity. Iphigenia can talk the hind leg off a donkey, and poor old Thoas (played with an intense listening stillness by Peter Guinness) doesn't stand a chance against her ardent torrent of persuasion.

Aidan McArdle's looks - huge dark-lashed eyes, full lips, black curly hair - come straight off a Greek vase. His Orestes is so dashing that it's a jolt to remember that the Greek prince is also quite insane: McArdle's rapid changes of register are frighteningly convincing and his brief foray into an (imagined) underworld, where he thinks he sees his murdered parents in the gloom, is chilling.

In the original, Iphigenia frees her brother and cousin by a stratagem, stealing the Taureans' treasured statue of Artemis in the process. Goethe's take on the story sees her unable to betray her saviour and shelterer Thoas, even when he's at his most unreasonable. Thoas, who got up that morning determined to drag the virgin priestess to his bed, is presented instead with an unwelcome and complex moral conundrum. But this play is so subtle and profound that it never becomes a mere question of civilisation versus barbarism.

'Under the Curse': The Gate, London W11 (020 7229 0706), to Saturday