The play is set in the Greek city of Argos before the palace of King Agamemnon. A watchman who is stationed on the roof of the palace delivers a monologue, explaining that Clytemnestra, Agamemnon’s wife and the Queen of Argos, ordered him to stand watch every night, looking out for the signal fires that will indicate the conquest of Troy by Agamemnon’s army. The watchman complains about the drudgery of his task. Suddenly, he sees the signal fires and rejoices. He sets out to deliver the news to Clytemnestra and cryptically expresses his hope that Agamemnon will truly return and set the city and his house in order. His lines hint at an unspoken apprehensiveness about the state of things in Argos under Clytemnestra.

As the watchman exits, the chorus, made up of Argive elders, enters the stage to sing its first song, the parodos. In a song spanning over 200 lines—the longest choral song of any surviving Attic tragedy—the chorus reflects on the events leading to the Trojan War and Agamemnon’s absence from his city. Agamemnon and his brother, Menelaus, “twin throned, twin sceptered, in twofold power / Of kings from god” (43-44) gathered a vast Greek army to fight against Troy after the Trojan prince, Paris, carried off Menelaus’s wife, Helen.