As the play opens, Iphigenia introduces herself. She is the daughter of Agamemnon and Clytemnestra, and she is offered as a sacrifice by her father so that his ships can set sail in spite of the storms and unfavorable winds in order to continue the quest for Helen of Troy.

Iphigenia tells us that Calchas, the soothsayer, reminded Agamemnon of his promise to sacrifice the year’s most beautiful maiden to Artemis. Odysseus was dispatched to trick Iphigenia by telling her that she was to marry Achilles, but instead she came to face to face with the knife that would slay her. However, at the last second, Artemis substituted a deer for Iphigenia and took the girl to a land ruled by King Thoas, run by Barbarians.

Now Iphigenia is a priestess who works for Artemis. She is responsible for the ritual sacrifice of all Greek intruders on Thoas’s shores. She explains that she doesn’t directly kill the victims, but she ordains them and fulfills the initiating rites before they are taken to the inner temple and the sacrifice is completed.

Iphigenia then tells of the dream she had the night before. She dreamed that she was home in Argos with her fellow maidens when her father’s house began to fall after a loud roll of thunder. The whole palace, except one column, fell to the ground. A man stood in the ruins, and Iphigenia began to perform the last rites that she so often has to do in her life as a priestess. Upon waking, she believes that this dream means her brother Orestes must now be dead. She tells us she will sadly pray in the temple for her brother.

We now see Orestes arrive with his friend Pylades and cautiously enter the temple of Artemis (the same temple Iphigenia serves). He asks Pylades if this is the temple they are looking for, and Pylades confirms. They see the blood of the Greeks who have been sacrificed and lament for those men, and Orestes also laments for himself and all he has been through. He has murdered his own mother to avenge his father’s death at her hands, and he has been pursued ever since by the Furies, making his life miserable.

Orestes talks about how the oracle Phoebus has told him to go to this temple and find the effigy of Artemis that fell from heaven and bring it to Athens. All Orestes knows is that if he can bring the statue to Athens, he will be free of his afflictions. But this task seems nearly impossible—the temple seems to be impenetrable. Pylades says they should leave the temple area and go and find a dark hiding place so that they aren’t captured. They are both afraid, but they have come this far, Pylades says; they can’t give up now. Orestes agrees, and they leave.

Some maidens appear, having apparently been summoned by Iphigenia, who tells them about her dream and her conviction that her brother Orestes is now dead. She wants the temple maidens to join her in making an offering in his honor. They join her, sympathizing about the plight of her family. Iphigenia, like Orestes, laments her beginnings and the unfortunate things that have happened to her. She isn’t living the life she was born to live, she says; instead she has to bear witness over and over again to the bloody deaths of the unlucky Greek foreigners.

Suddenly, a man approaches with news of two young Greek men who must be sacrificed. The audience knows they must be Orestes and Pylades, but although the messenger heard Pylades’s name, he doesn’t know the other man’s name. Yet he knows they are both strong and brave—godlike, even. Iphigenia tells the messenger to go back and have the soldiers bring the two young Greeks to her. She is usually compassionate and doesn’t like having to fulfill her role, but feeling angry and wretched about the death of her brother, she is prepared to be cruel and violent this time.

When the men arrive, Iphigenia asks them if there are women in their families who will miss them or grieve them when they are gone. Orestes tells her she shouldn’t worry about all of that—he and Pylades knew the risk they were taking when they decided to undertake the mission. He refuses to tell her his name or any other details about himself, but he does tell her some details about what has happened in Troy: how it has fallen and how Helen has returned to Sparta. They share their mutual hatred for Helen and their grief about all that has happened, but Orestes is mystified about why Iphigenia knows—or cares—so much about all of it.

Iphigenia tells Orestes she is from Hellas as well, but they continue to conceal their respective identities. He reveals that Orestes is still alive, though, which naturally changes her whole outlook. She asks him, if she lets him go alive, will he take a letter to Argos for her? He says that Pylades can go instead. He wants to save Pylades, since Pylades is an innocent bystander.

He asks Iphigenia what her part in the sacrifice will be, and when she tells him that she will perform the rites beforehand, he says that he wishes his sister were there to cover his body after he is dead. Iphigenia promises to do that for him.

Pylades doesn’t want to leave his friend, but Orestes assures him it’s the right decision, saying that he has to atone for what he has done to his mother. He wants Pylades to marry Electra, his and Iphigenia’s other sister, and then build a temple for him (Orestes).

When Iphigenia brings the letter, she reveals it is for Orestes, who then finally tells her who he is. At first, she doesn’t believe him, but he gives her some details about their upbringing that no one else would know. Once she is convinced, he explains that he needs to take the statue and why, and Iphigenia hatches a plan to escape. She tells Thoas, the ruler, that she must cleanse the two men and the statue in the sea before the sacrifice. She adds that they are so unclean that the other citizens had better stay inside while all of this is happening.

Once she and the two men are down at the shore, she tells the guards to look away, ostensibly so that they are not tainted, but it is known to us that she and the two men will make their escape. The guards disobey and sound the alarm. Thoas’s men try to capture them and fail at first because the three are able to keep them at bay. However, as they escape and sail away, a vicious wind pushes them back, where they are captured. However, the goddess Athena appears to Thoas and tells him that since Orestes was told to take the statue by the Oracle of Delphi, he must let Orestes carry out the plan and set up the statue in a temple in Argos. Thoas agrees, and the three return to Argos; Orestes is now free of the Furies, and Iphigenia is a priestess of an Artemis temple in Brauron.