Gluck's Successful Sequel: Iphigenia in Tauris
ACT ONE begins five years after the Trojan War. Back in Aulis, at the end of Gluck's earlier opera Iphigenia in Aulis, Iphigenia's father Agamemnon had intended to sacrifice her to the gods, in exchange for good battle weather. But her life was saved by the goddess Diana.
Now, Iphigenia is serving as a priestess among her enemies, the rather barbaric Scythians, in Tauris. Her mother, Clytemnestra, has killed Agamemnon, and her brother Orestes has killed Clytemnestra in revenge. Iphigenia doesn't yet know any of this, but does describe a dream in which both of her parents are dead, and she herself is forced by a "fatal power" to kill Orestes.
Thoas, the Scythian king, has a vision of his own -- a premonition that a foreigner will murder him. So when two strangers are brought in, he orders Iphigenia and her priestesses to sacrifice them.
In ACT TWO, when Iphigenia meets the prisoners, she can't help but notice that one of them bears a strong resemblance to her brother Orestes. Of course, it is Orestes. But neither one of them figures that out for quite some time. The other stranger is Orestes' friend, Pylades. When the two prisoners are alone, Orestes is tortured by the Furies, who have hounded him ever since he killed his mother.
Iphigenia and Orestes then talk together -- but without recognizing each other. Iphigenia finds out that Orestes is from back home, in Greece, and asks for news of King Agamemnon and his family -- that is, for news of her own family. Orestes tells her what happened, but doesn't tell her who he is. Instead, he says that everyone in the king's family is dead, except Iphigenia's sister Elektra. Iphigenia mourns for her supposedly dead brother, and the second act ends.
As ACT THREE begins, despite Thoas's order, Iphigenia decides to allow one of the two prisoners to go free. She hopes it can be Orestes, as she has grown fond of him. But Orestes has felt he was going mad ever since he killed Clytemnestra. So he urges Pylades to go, feeling he himself is better off dead. Reluctantly, Pylades agrees to escape, with Iphigenia's help.
In ACT FOUR, it's finally time for Iphigenia to go through with the sacrifice, and kill Orestes. But at the sacrificial altar, they finally recognize one another. When Thoas finds out who his priestess and the prisoner really are, he decides to kill them both. But just then Pylades returns with an army of Greeks. The two sides battle until the goddess Diana appears. She puts a stop to the fighting, and grants Iphigenia and Orestes a safe passage home.