In Greek mythology, Ismene was a daughter of Oedipus and Jocasta and sister to Antigone. She appears in several plays of Sophocles, at the end of Oedipus the King and to a limited extent in Oedipus at Colonus and Antigone.
When Oedipus stepped down as King of Thebes, he gave the kingdom to his two sons, Eteocles and Polynices, who both agreed to alternate the throne every year. However, they showed no concern for their father, who cursed them for their negligence.
After the first year, Eteocles refused to step down and Polynices attacked Thebes with his supporters (the Seven Against Thebes). Both brothers died in the battle. King Creon, who ascended to the throne of Thebes, decreed that Polynices was not to be buried.
However, the sister of Polynices, Antigone, defied the order and was caught. In spite of her betrothal to his son Haemon, Creon decreed that she was to be buried alive. Antigone's sister Ismene then declared she had aided Antigone and wanted the same fate, though she did not participate in the crime. Antigone refuses to let her be martyred for a cause she did not stand up for. The gods, through the blind prophet Tiresias, expressed their disapproval of Creon's decision, which convinced him to rescind his order. He then went to bury Polynices himself.
Unaware of Creon's change of heart, Antigone had already hanged herself rather than be buried alive. When Creon arrived at the tomb where she was to be interred, Haemon attacked him and then killed himself. When Creon's wife Eurydice was informed of their deaths, she too took her own life.