The scene is laid partly within and partly without the palace of Agamemnon at Argos or Mycenae, on the day of the return of the king from his long absence at Troy, beginning in the period of darkness just preceding the dawn.
The blood-feud between Atreus and Thyestes was not ended with the terrible vengeance which Atreus wreaked upon his brother. It was yet in fate that Thyestes should live to beget upon his own daughter a son, Aegisthus, who should slay Atreus and bring ruin and death upon the great Atrides, Agamemnon.
The Trojan war is done. And now the near approach of the victorious king, bringing his captives and treasure home to Argos, has been announced. But little does he dream to what a home he is returning. For Clytemnestra, enraged at Agamemnon because he had sacrificed her daughter Iphigenia at Aulis to appease the winds, and full of jealousy because he brings Cassandra as her rival home, estranged also by the long-continued absence of her lord, but most estranged by her own guilty union with Aegisthus, is now plotting to slay Agamemnon on his return, gaining thus at once revenge and safety from his wrath.
ACT I
Ghost of Thyestes: Escaped from gloomy Pluto's murky realm
And leaving Tartara's deep pit I come,
All doubting which abode I hate the more;
That world I flee, but this I put to flight.
My soul shrinks back, my limbs do quake with fear.5
I see my father's house—my brother's too!