Dionysus, the god of wine, prophecy, religious ecstasy, and fertility, returns to his birthplace in Thebes in order to clear his mother's name and to punish the insolent city state for refusing to allow people to worship him. The background to his return is presented in the prologue, in which Dionysus tells the story of his mother, Semele, once a princess in the royal Theban house of Cadmus. She had an affair with Zeus, the king of the gods, and became pregnant. As revenge, Zeus's jealous wife Hera tricked Semele into asking Zeus to appear in his divine form. Zeus, too powerful for a mortal to behold, emerged from the sky as a bolt of lightning and burnt Semele to a cinder. He managed, however, to rescue his unborn son Dionysus and stitched the baby into his thigh. Semele's family claimed that she had been struck by lightning for lying about Zeus and that her child, the product of an illicit human affair, had died with her, maligning her name and rejecting the young god Dionysus.