Cacoyannis adapted the film, the third in his "Greek Tragedy" trilogy (after the release of Electra in 1962 and The Trojan Women in 1971), from his stage production of Euripides' play Iphigenia at Aulis.

Agamemnon, Menelaus' brother and the King of Argos, gathered a large Greek expedition at Aulis to retrieve Helen.

However, Artemis, angered by an offense from Agamemnon's father, King Atreus, caused storms to hinder the Greek fleet.

This angers Calchas (Dimitris Aronis), the high priest of Artemis' temple, who delivers an oracle to Agamemnon in the presence of Menelaus (Kostas Karras) and Odysseus (Christos Tsagas).

According to Calchas, the oracle, believed to be from Artemis herself, demands that Agamemnon offer a sacrifice to atone for the defilement of the holy ground and the killing of the sacred stag.

In the letter, Agamemnon requests that his wife send their daughter, Iphigenia, alone to Aulis, supposedly to marry Achilles (Panos Mihalopoulos).

After admitting his deception to his old servant (Angelos Yannoulis), Agamemnon sends him with another letter to Clytemnestra, revealing the deal and urging her to cancel Iphigenia's journey.

In a poignant scene reminiscent of the dying sacred stag at the film's outset, Iphigenia is found lying exhausted and breathless on the forest floor, evoking a sense of impending tragedy.

With a strong wind now blowing, the men hasten to the beach, launching their ships into the sea and setting sail towards Troy and its promised riches.

Cacoyannis made a number of changes to Iphigenia at Aulis in order to adapt it to modern cinema, some of them significant divergences from the original plot.

He introduces as dramatis personae Odysseus and Calchas, who were not present but were mentioned in the original play, to further the plot and voice certain themes.

In the film, there is no overt reference to this event: the audience sees clouds and mist, followed by a shot of Agamemnon's shocked expression.