After their daring escape from Syrellian castle and the Mad King Varan, Cari settles into her life in Piscea with her sisters. Each of the merfolk kingdoms face challenges as they prepare for the repercussions. In Zephyrial, Prince Evander marries the mermaid his parents promised him to when he was young, and adjusts to life as a husband.

Prince Kallan works toward regaining control of his kingdom and looking after his family. His plans to rescue Adamaris from Syrellian before his father figures out that he is the one leaking information to help the other kingdoms evade attacks. Meanwhile, Adamaris struggles with looking after his little sister, betraying his father, and learning long-buried secrets that paint a terrifying picture of their kingdom's history.

And the Sea Witch continues to pull strings, endeavoring to shift things in her favor by making friends with Evander's new bride, Lady Eunji.