Juptiter caught word of this and wanted to protect her so he sent his son Mercury to distract Argus. Mercury sang songs and told stories so that Argus would fall asleep and close all of his many eyes. Once he had fallen asleep, Mercury killed him and freed Io to send her home, still in the form of a cow. Angry that her plan was foiled, Juno sent a gadfly to sting Io forever. Only when Jupiter vowed to no longer pursue Io did Juno transform Io back into a human and free her from the gadfly.
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