Io was the priestess to Hera, wife of the thunder god Zeus. Zeus took a liking on her, and to avoid detection from his jealous wife, he shrouded the place where he seduced Io with clouds. Naturally, Hera was suspicious of the cloud's formation as well as Zeus' apparent absence from Mount Olympus. When she descended, she found Zeus as a white cloud alongside a beautiful heifer. Hera knew full well that the heifer was Io, turned by Zeus, and to trap him Hera demanded Zeus the heifer as a present. Zeus had no choice but to present heifer Io to Hera, who set the multiple-eyed giant Argus Panoptes to guard her. Zeus then sent Hermes to lull Argus to sleep, and in that moment set Io free, where she roamed all the way to Egypt.