The opera begins in the early morning following a battle in Thebes between the armies of the two sons of Oedipus: Eteocles and Polynices.
They are known to frequently eat large whelks (Buccinum), cockles (Polynices, Chrysodomus and Sipho), sea clams (Mactra), large hermit crabs, starfish, sea urchins and green crabs (Carcinus maenas).
In this version of the myth, however, Argia, Polynices's wife, persuades her husband to give the necklace to Eriphyle so that Amphiaraus will join the war effort.