Atalanta and Damien are the last descendants of the mythic figures of Medusa and Perseus. Their divine blood is not the only thing they have in common--they are mortal enemies locked in a centuries long feud. One that would have ended if not for the interference of a priestess with a vague prophecy of world-destroying events that only they can prevent.

They must set aside their hatred long enough to travel from the shores of Sicily to the island of Crete to find answers.

The tumultuous changes of the end of the 15th century darken the edges of their journey as they learn to navigate the strange juxtaposition between old oaths and new.

A year after Atalanta and Damien were brought together by the Pythia, they are once more called together. All around the Mediterranean there are strange storms, mysterious disappearances, and gruesome murders. Though the events are seemingly unrelated, Calista is convinced they are the work of Poseidon. She tasks Atalanta and Damien to put an end to the destruction. With old allies and new, they must face sea monsters, pirates, fearful mortals, and sirens on their way to finding, and stopping, Poseidon.