The action of Elektra is the bloody culmination of a Greek family tragedy at the heart of the Trojan War. The roots of the tragedy lay in the marriage of two brothers, Agamemnon and Menelaus (sons of King Atreus), to two sisters, Klytemnästra and Helen. When Helen was abducted by Paris, son of the King of Troy, Menelaus, Agamemnon and their Greek forces fought to free Helen and restore the national honor— the storied Trojan War. At the war’s end, Menelaus and Helen fled to Egypt, while Agamemnon returned to Mycenae. There he found that Klytemnästra had taken a lover, Aegisth. Klytemnästra proceeded to murder Agamemnon and make Aegisth her consort. The three royal children — Elektra, Chrysothemis, and Orest— vowed to avenge their father’s murder.

As the opera opens, Elektra is working as a servant in the palace of Agamemnon, murdered king of Mycenae. Other servant girls comment on her strange behavior. Obsessed with the memory of her father’s murder, Elektra evokes his spirit and swears to dance triumphantly over the bodies of his killers. Her younger sister, Chrysothemis, warns that Klytemnästra is planning to imprison Elektra and begs her to cease threatening their mother so they might lead normal lives as wives and mothers. As the queen approaches, Chrysothemis begs Elektra not to incite her.

Klytemnästra confides that she is tormented by terrible dreams and asks how to escape them. Elektra explains that her mother has been making the wrong sacrifices. Pressed for the answer, Elektra screams that the required sacrificial victim is Klytemnästra herself. Terrified at first, the queen’s countenance changes to glee when her maid whispers a message.

When Chrysothemis brings news that Orest is reported dead, Elektra understands her mother’s mood change. The two sisters must themselves kill the guilty rulers now, but Chrysothemis flees. Undaunted, Elektra begins digging for the ax she buried earlier for Orest’s use. As she is searching, a stranger appears. It is Orest, but he does not recognize his own sister nor she him at first. “The dogs of the house know me,” he says, ”but not my own sister!” Crying his name, Elektra falls into Orest’s arms, rejoicing that he has returned to avenge their father. After he enters the palace, Klytemnästra’s agonized screams are soon heard. Arriving back at the palace, Aegisth is puzzled by Elektra’s giddy behavior. She sends him inside, but he quickly appears at a window screaming for help. ”Agamemnon hears you!” exults Elektra. Chrysothemis too rejoices in Orest’s deed. But Elektra, ecstatic in this moment of triumph, dances frenziedly before collapsing lifeless.