Io was taken by Hera and placed under the guard of Argus, a monstrous being that had 100 eyes. This was so that he would never lose watch, as half his eyes could sleep while the other half remained open. Both portions of each day, therefore, would pass under guard.
After a long passing of time, Zeus sent His messenger Hermes to liberate Io. The God took along His flute and made friends with Argus, eventually sending the guardsman into a complete sleep for the first time with His music and songs only known in the heavens, Divine power in all the notes. Finally, with all of his eyes closed, Hermes drew His sword and killed him. Io was finally free, and thus, Hermes was known as the Slayer of Argus.
Hera relinquished Her hold on Io, but still felt the need to honor Argus for his loyalty. Taking all of his eyes, She put them on the tail of the peacock, which became Her sacred bird. Still today, the gorgeous animal possesses 100 to 130 "eyes" on its feathers.
Io continued her journey, now as the life of a cow. To mark the course of her land travels, the Ionian Sea took her name, and also the Bosphorus, which means Ford The Cow. Io eventually reached the Nile River where Zeus restored her to human form. Together they had a child named Epaphus.
