The myth's outline is that Zeus had seduced Io when Hera arrived on the scene. Zeus transformed Io into a cow to hide his infidelity, but Hera was not deceived. When Hera asked, Zeus was obliged to give her the cow. Hera appointed her servant Argus to guard the cow, and Hermes, at Zeus' command, killed Argus. The detail omitted in this summary varies depending on which source is referenced. Two prominent sources of the myth of Argus's death are Aeschylus's play Prometheus Bound (c. 500 BCE) and Ovid's Metamorphoses (c. 8 CE).
In Prometheus Bound Io, as a cow, has been wandering all over Greece desperately fleeing from a stinging gadfly ever since Hermes killed Argus. She comes upon Prometheus and relates her story in exchange for a prophecy. According to Aeschylus, the ghost of "Argus --that evil thing-- / The hundred-eyed- / Earth born herdsmen" (617-9) was the gadfly sent by "Hera's curse... [to pursue Io] ever on [her] endless round" (657-8). Little else is revealed about Argus in the play, as Io focuses on her wanderings. The play presents the myth in a manner that suggests it should be familiar to the audience, revealing only the details that are pertinent to the themes of the play.
Unlike Aeschylus, who assumes knowledge of the myth and omits details such as Argus' death at the hand of Hermes, Ovid tells a complete narrative of one version of this myth in the Metamorphoses. According to Ovid, Argus had "the hundred eyes / All watching and on duty round his head, / Save two which took in turn their sleep and rest" (I.625-7). The following lines tell that Zeus dispatched Hermes to slay Argus and set Io free. Hermes sang Argus to sleep, used his magic wand to seal Argus's eyes shut, and decapitated Argus. Hera was furious about the death of her servant Argus, and "Juno [Hera] retrieved those eyes to set in place / among the feathers of her bird and filled / his tail with starry jewels" (I.721-3), creating the eyes of the peacock. Furthermore, Hera, "before her rival's [Io's] eyes and in her mind... set a frightful Fury" (I.725-6).
Sources with different details for the same myth are characteristic of Greek myth, which is rooted in oral transmissions. Notice that in Ovid's tale Hera does not dispatch the ghost of Argus to torment Io as a gadfly. Hera calls upon a Fury as she does in an episode in Virgil's Aeneid that recounts Hera enlisting a Fury to torture the wife of Latinus. In Prometheus Bound, Argus is the child of Gaia, but Ovid is silent on the issue of Argus's lineage. While Ovid and Aeschylus give Argus one hundred eyes, other traditions, according to Pierre Grimal, attribute one eye or four eyes to the monster Argus. Just as there are differences in the literary preservation of this myth, representations of Argus in the plastic arts may differ. For example, Ovid describes Argus with one hundred eyes in his head, but an Attic vase (c. 490 BCE) depicts Argus with eyes all over his body (Powell 375).