Madness of Heracles.
Returning to Thebes from Mount Cithaeron, Heracles (Hercules) led the Theban citizens in battle against the Minyans of Orchomenus, to whom they had been forced to pay tribute. King Creon rewarded Heracles with the hand of his daughter Megara; the couple married and had three children. [Some ancient authors say there were eight children.] Some years later, Hera caused Heracles to suffer a fit of madness, during which he killed his children (and his wife, according to some classical sources). It is said that Heracles also killed two nephews, sons of Iphicles. [The cause for Hera's intervention, according to some ancient sources, was her desire to force Heracles into servitude to Eurystheus, and his defilement with his family's murder would require some expiation.] When he regained his sanity, Heracles went into exile and visited the oracle at Delphi to learn how he might expiate his crime. He was told to go to Tiryns and serve King Eurystheus for twelve years. According to Euripides’ version of the myth, the madness of Heracles and the disastrous results of it occurred after he had performed his twelve labors for Eurystheus.
    
     For Further Reference: G.K. Galinsky (1972), The Herakles Theme (Totowa, NJ: Rowman & Littlefield), 192-93 and 232-33.