One day, Zeus the king of the gods saw a beautiful mortal named Io. He descended to Earth to pursue her and conjured a single storm cloud to hide himself and the object of his affection from his wife Hera.

But Hera knew her husband well and knew what he was up to as soon as she saw the cloud. To avoid his wife's fury he changed Io into a white cow. Hera, playing along, demanded the beautiful cow for herself.

Hera knew the cow was a woman who had tempted her husband so she held her captive under guard of her giant servant Argos. Argos had one hundred eyes and never closed all of them at once

Zeus, feeling guilty and worried about Io, sent his son Hermes to set her free.  Hermes disguised himself as a shepherd and played slow music and told Argos boring stories all day and night until he closed all of his eyes and fell into a deep sleep.  Io escaped, Hermes killed Argos and Hera took Argos's eyes and placed them on the tail of her favorite bird the peacock

In her fury, Hera sent a gadfly to torment Io. She ran around the world trying to rid herself of the terrible fly.

By the time Io got to Egypt Zeus pleaded with his wife to finally leave her alone.  Hera complied, Zeus changed Io back to her human form, and she stayed in Egypt where she went on to be worshipped as the goddess Isis.