The scene has changed to the outside of Agamemnon's palace at Argos. Orestes and Pylades knock at the door. A servant answers. Orestes tells him that they are travelers with an important message and are seeking a place to stay for the night.
The servant calls Clytaemestra. She comes to the door and welcomes the strangers. After offering them the hospitality of the palace, she asks to hear their message. Orestes says that he and his companion are Daulian merchants, just arrived in Argos from Phocis. On the road to Argos, they encountered Strophius, the king of Phocis, who asked them to inform the parents of Orestes that their son was dead. Clytaemestra begins to lament for the dead Orestes, then invites the two "merchants" to come inside.
A moment later, Cilissa, an old woman who was Orestes' nurse when he was a child, comes out of the palace. She tells the chorus that Clytaemestra has sent her to tell the news to Aegisthus and bring him back to the palace to question the strangers. She accuses Clytaemestra of affecting grief for the sake of appearances and begins tearfully to reminisce about Orestes as an infant. The old nurse says that the news of the death is the hardest blow she has yet had to endure in her long life. She adds bitterly that Aegis-thus, the defiler of the House of Atreus, will be glad to hear this sad news.
The chorus ask whether Clytaemestra's message advises Aegisthus to return to the palace accompanied by his usual bodyguard of soldiers. Cilissa replies that these were Clytaemestra's instructions. The chorus tell her to withhold this part of the message so that Aegisthus will return alone. Cilissa is puzzled but agrees to do as they ask.
Clytaemestra's warm welcome to the strangers has a special irony because it calls to mind her welcome to Agamemnon in the first play of the trilogy; this association puts her murder by Orestes into a category as morally ambiguous as her own crime. Her lament for Orestes is moving and seems genuine until Cilissa reveals that Clytaemestra's grief is false and that she is really overjoyed at the news. The self-control and fast thinking behind Clytaemestra's pretense show that she is essentially the same woman she was in Agamemnon.
The naturalistic characterization of Cilissa has been praised by many critics. She has several important functions. Her sincere grief serves as a standard by which to measure Clytaemestra's affected sorrow and secret joy. There is also a striking contrast between the innocent baby described by the nurse and the unhappy man that fate has made of Orestes.
In this scene, the chorus steps out of its usual role as spectator and commentator to take a part in the intrigue leading up to the killing of Aegisthus and Clytaemestra. The elimination of the soldiers who normally escort Aegisthus is an essential contribution to Orestes' success.