Juno and Io
This Greek myth about flirting, deceit, some wrath and then some mercy involves Juno and her husband Jupiter (Zeus in Greek mythology), the water nymph (a type of lower goddess) Io, who is the daughter of the water god Inachus, Mercury (Hermes in Greek mythology), and Argus (a giant with one hundred eyes).
It starts with Juno looking down on Earth from heaven and seeing an unusual dark cloud. She assumes that the cloud was put there by her husband to hide himself. Juno blows the cloud away and goes down to investigate. She finds her husband Jupiter standing by a river with an attractive heifer (a female cow). Jupiter had been flirting with a river goddess named Io and when he sensed his wife coming, changed Io into a heifer.
Juno compliments the beauty of the heifer and asks who it belongs to. Jupiter says it was a “new creation of the Earth” and didn’t belong to anyone. Then Juno asks to have the heifer. Jupiter can’t say no because it would look suspicious so he gives the heifer to his wife.
Juno senses something is going on with the heifer so she gives it to Argus, the giant with one hundred eyes, to keep a close watch over it. Argus agrees and begins watching the heifer. Io’s (the heifer’s) father and brother come across Io in her transformed state and offer it some grass to eat. Io licks her father’s hand but he doesn’t understand. Then Io writes her name in the dirt with her hoof and he understands and is sad that she’s been changed into a female cow. Just then Argus comes near and chases her father Inachus, the river god, away from Io.
At this point Jupiter becomes sad about Io being changed into a heifer and her being held under so close a watch by Argus. He decides to call on Mercury who is the Roman god (his name is Hermes in Greek mythology) of trade and poetry and actually a lot of other things, to go and lull Argus to sleep and then kill him. Mercury agrees and leaves heaven with his winged shoes and lands on Earth. He leaves his shoes and cap and only takes his syrinx, which is a reed-like instrument, and poses as a shepherd playing music.
Argus hears and likes the music he is playing and invites him over to rest and play more. Mercury agrees and plays his most calming songs and lulls most of Argus’s eyes to sleep but a few stay open. Then, to lull the giant all the way to sleep, he tells the story of how the syrinx came to be. In short, there was a river goddess named Syrinx and she was beautiful. Pan, the god of the wild and shepherds and flocks, saw her and wanted to marry her. Syrinx runs away and Pan chases. She runs right up to the river and then asks the other water nymphs (goddesses) to help her. They change Syrinx into reeds just as Pan arrives. He is sad she has been changed but likes the music the reeds make. He cuts a few and begins to play them as an instrument and is happy to at least have the instrument, if not Syrinx herself.
That story lulls Argus all the way to sleep and Mercury chops off his head, killing him and freeing Io, still in heifer form. Juno, however, is still upset and has further plans of torment for Io. She sends a gadfly, which is a fly that bites horses, to chase and torment her. Io runs all over the world and through oceans to escape the gadfly. Finally, after promising not to go down and flirt with Io anymore, Jupiter convinces his wife Juno to change Io back into her original form and reunite her with her family, which she does.