Seventeen-year-old Gen may have rescued her beloved father from prison, but she hasn't saved him yet. If she fails her end of a bargain with the Olympian Empresses, they will send him right back to his cell. To keep the Empresses happy, Gen must bring them the legendary golden apples of Hesperides and the monstrous Cerberus. But both are rumored to be in the neighboring Elysium Empire, which has a long history of war with Olympia. Making matters worse, Gen's former enemy and newly designated heir to the isle of Arcadia Castor invites herself on the journey, hoping a golden apple could end Arcadia's reliance on Illumium for storm vials. And Castor's twin brother, Gen's StormMaker boyfriend Pollux, has been pulling away from Gen due to troubles stemming from her mind magic. With Castor's pirate-thief girlfriend and Pollux's servant companion in tow, the unlikely team embarks on its voyage. But war is only an insult away in Elysium, and more than the Emperor has their eyes on Gen's mission.

The quest has caught the attention of one of Elysium's Oracles, and trouble is sure to brew with Prophecy on the rise.