The jealous wrath of Juno, working through Eurystheus, has imposed twelve mighty and destructive tasks on Hercules, her hated stepson. But these, even to the last and worst, the bringing of Cerberus to the upper world, he has triumphantly accomplished. Abandoning her plan of crushing him by toils like these, she will turn his hand against himself, and so accomplish his destruction. Upon the day of his return from hell, she brings a madness on him, and so precipitates the tragedy which forms the action of the play.