Check out this full version of the story from our Number One Narrator, Thomas Bulfinch.
Agamemnon, the general-in-chief of the Greeks, the brother of Menelaus, and who had been drawn into the quarrel to avenge his brother's wrongs, not his own, was not so fortunate in the issue. During his absence his wife Clytemnestra had been false to him, and when his return was expected, she with her paramour, Aegisthus, laid a plan for his destruction, and at the banquet given to celebrate his return, murdered him.
It was intended by the conspirators to slay his son Orestes also, a lad not yet old enough to be an object of apprehension, but from whom, if he should be suffered to grow up, there might be danger. Electra, the sister of Orestes, saved her brother's life by sending him secretly away to his uncle Strophius, King of Phocis. In the palace of Strophius Orestes grew up with the king's son Pylades, and formed with him that ardent friendship which bas become proverbial. Electra frequently reminded her brother by messengers of the duty of avenging his father's death, and when grown up he consulted the oracle of Delphi, which confirmed him in his design. He therefore repaired in disguise to Argos, pretending to be a messenger from Strophius, who had come to announce the death of Orestes, and brought the ashes of the deceased in a funeral urn. After visiting his father's tomb and. sacrificing upon it, according to the rites of the ancients he made himself known to his sister Electra, and soon after slew both Aegisthus and Clytemnestra.
This revolting act, the slaughter of a mother by her son, though alleviated by the guilt of the victim and the express command of the gods, did not fail to awaken in the breasts of the ancients the same abhorrence that it does in ours. The Eumenides, avenging deities, seized upon Orestes, and drove him frantic from land to land. Pylades accompanied him in his wanderings and watched over him. At length, in answer to a second appeal to the oracle, he was directed to go to Tauris in Scythia, and to bring thence a statue of Diana which was believed to have fallen from heaven. Accordingly Orestes and Pylades went to Tauris, where the barbarous people were accustomed to sacrifice to the goddess all strangers who fell into their hands. The two friends were seized and carried bound to the temple to be made victims. But the priestess of Diana was no other than Iphigenia, the sister of Orestes, who, our readers will remember, was snatched away by Diana at the moment when she was about to be sacrificed. Ascertaining from the prisoners who they were, Iphigenia disclosed herself to them, and the three made their escape with the statue of the goddess, and returned to Mycenae.
But Orestes was not yet relieved from the vengeance of the Erinyes. At length he took refuge with Minerva at Athens. The goddess afforded him protection, and appointed the court of Areopagus to decide his fate. The Erinyes brought forward their accusation, and Orestes made the command of the Delphic oracle his excuse. When the court voted and the voices were equally divided, Orestes was acquitted by the command of Minerva.
One of the most pathetic scenes in the ancient drama is that in which Sophocles represents the meeting of Orestes and Electra, on his return from Phocis. Orestes, mistaking Electra for one of the domestics, and desirous of keeping his arrival a secret till the hour of vengeance should arrive, produces the urn in which his ashes are supposed to rest. Electra, believing him to be really dead, takes the urn and, embracing it, pours forth her grief in language full of tenderness and despair.