The great Honsu decides, after seeing Atlan's proof of human life on the surface, to attack before the surface-dwellers grow strong enough to pose a threat. And attack he does. And slaughter. And destroy. Until he reaches Egypt, where the threat is the sun, and the lack of water is the downfall.
His son Haumond is left behind in the retreat, and meets a descendant of one of the original explorers from the newly sunken Atlantis. Honsu believes him to be dead, and Haumond no longer cares what Honsu thinks. Learning that the descendants from Atlantis now rule in many lands, he formulates a plan to end the death caused by his father.
Due to the "death" of his son, Honsu decides to avoid dry Egypt and tackle... Greece.