One day, as Zeus was sitting high up on his Olympian throne he spotted a beautiful young priestess named Io. He came down to her, and was so awed by him that she fell in love with him immediately. Now, Io was a priestess in the temple of Hera, Zeus' wife, so if Zeus and Io were caught together Io could expect not to live a long nor happy life. Their affair lasted for quite sometime, but, as always, Hera became suspicious of Zeus' "innocent" actions. Fearing for Io's life, Zeus changed the girl into a beautiful white cow. Hera, knowing what Zeus had done, asked for Zeus to give her the cow. Not having much of a choice (who'd want to go against Hera?) Zeus did as his wife asked. Hera, not really wanting to keep Zeus away from the cow herself asked Argus to guard Io. Now, Argus was perhaps the best guard in Ancient Greece, for he had 100 eyes, and never needed to close them all in sleep at one time. He could, in essence, watch his charge all of the time. Hera told Argus to let Io wander as she wanted, as long as she kept away from Zeus, and wander she did, giving her name to the Ionian gulf. Soon, though, she grew tired of her restless ways and settled down.
Zeus, still feeling sorry for what he had done asked Hermes to lull Argus to sleep and steal Io away (some myths claim that Zeus had come to Io in the shape of a bull, and made her pregnant. Zeus didn't want Hera to discover his little secret, and that was the reason for his helping poor Io). Hermes lulled the giant to sleep and killed him, so he would not follow once he had woken up. Hera was very upset when she discovered what had happened, and placed Argus' eyes on the tail feathers of the peacock. Not quite finished with Io, Hera sent a horsefly to drive the cow crazy. The fly drove Io to Egypt, where Zeus found her and turned her back into a human. She soon gave birth to a son, Epaphus. Still in a jealous rage, Hera abducted Epaphus, and Io spent the rest of her days looking for him. Some scholars say she found him and returned to Egypt, where she became the goddess Isis.