Thyestes then consulted the oracle at Delphi about how to get even. He was told to father a child on his own daughter Pelopia. So Thyestes ravished her in darkness, but she managed to get his sword. Having put Aerope away, Atreus went searching for a new wife and found Pelopia, who in time gave birth to Aegisthus. Thinking that the boy was his own, Atreus accepted him as his son.
A famine plagued Mycenae because of Atreus' revenge. It could be allayed only by Thyestes' return from exile, so Atreus sent for his brother, pretending reconciliation. When Thyestes arrived Atreus imprisoned him and sent Aegisthus to kill him. Thyestes recognized that Aegisthus' sword was his own, so he overpowered his son by Pelopia and bade him bring his mother. When Pelopia came to Thyestes' cell Thyestes revealed himself as her father and ravisher, whereupon Pelopia killed herself with the sword. Aegisthus then realized that Thyestes was his natural father, and in filial devotion he slew Atreus, who had raised him since infancy. Thyestes became the king of Mycenae again, while Atreus' sons, Agamemnon and Menelaus, went into exile.
The two brothers solicited the help of King Tyndareus of Sparta, who marched on Mycenae and restored Agamemnon to the throne of a rich and powerful state. By killing a cousin, Agamemnon acquired Clytemnestra, Tyndareus' daughter, as his wife. Menelaus married the beautiful Helen, and Tyndareus allowed him to rule Sparta. However, a Trojan prince named Paris abducted Helen, which precipitated the Trojan War. Agamemnon became the head of the Greek forces and left Mycenae for ten years to fight the Trojans. His wife Clytemnestra had little love for Agamemnon. He had killed her first husband, sacrificed their daughter Iphigenia to Artemis to allow the Greek fleet to sail, and taken a number of mistresses. To avenge herself Clytemnestra took her husband's arch-rival, Aegisthus, for her lover, and with him she plotted Agamemnon's death. When her husband returned victorious from Troy Clytemnestra greeted him warmly, although he had brought Cassandra, his foreign mistress, home with him. At the banquet given in honor of his homecoming, Aegisthus slaughtered Agamemnon as Clytemnestra murdered Cassandra. Aegisthus' forces were triumphant in defeating the king's supporters, and Aegisthus took over Mycenae and ruled it with Clytemnestra.
