Io, daughter to Inachus, beloved by Zeus who in order to conceal her from his jealous wife Hera, changed Io into a heifer. Hera set Argus, the hundred eyed monster to watch her (supposidly so Io couldn't change back to human form) and Zeus sent Hermes to kill Argus. Hera then had Io tormented by a gadfly that drove her to swim across the Ioian sea to Egypt. There she resumed her human form and bore a son, Epaphus.