When her sister Helen and wife of Agamemnon's brother, Menelaus, was abducted by Paris and was taken to Troy, Agamemnon decided to help his brother and bring his wife back, thus starting the Trojan War. Before the army left for Troy, Agamemnon was forced to sacrifice his daughter Iphigenia, as he had caused the wrath of Artemis. While he was away, Clytemnestra started an affair with Aegisthus, with whom she plotted against her husband. Clytemnestra was angry with her husband, both because of her daughter's sacrifice, as well as because Agamemnon had killed her first husband and taken her by force.
Upon his return from Troy, Agamemnon was welcomed by his wife. When he went to take a bath, Clytemnestra threw a net on him and stabbed him. Agamemnon's concubine, Cassandra, who was outside the palace, had foreseen the plot, but as she was cursed by the god Apollo, no one believed her and she reluctantly accepted her fate and was slain.
Aegisthus and Clytemnestra took the rule of Mycenae for seven years, until Orestes, the son of Clytemnestra and Agamemnon, returned and killed his mother and her lover as revenge for his father's death.