The Furies...the Roman name (Furiae) for the Greek Erinyes, said by Hesiod to have been the daughters of Gaia (Earth) and to have sprung from the blood of Uranus, and by other accounts to be the daughters of Night , or of Earth and Darkness. They were three in number: Tisiphone (the Avenger of Blood), Alecto (the Implacable) and Megaera (the Jealous One). They were the merciless goddesses of vengeance and punished all transgressors, especially those who neglected filial duty or claims of kinship. Their punishments continued after death.

Orestes...in Greek legend the son of Agamemnon and Clytemnestra, who killed his mother and her lover Aegisthus in revenge for their murder of his father....in Aeschylus' Oresteia...he hesitates to kill Clytemnestra but is pressurized into doing so by Apollo, his sister Electra and the chorus. He is then driven mad by the Furies who demand that he be tried for his crime. He is finally acquitted by Athene.

from Brewer's Dictionary of Phrase and Fable.

Painting: W Bouguereau Orestes and the Furies