Airie is the reluctant heiress to the bankrupt Finnder family, Alena is the crazy mermaid of the Lagunov clan that Airie has somehow fallen in love with. To escape her troubles on shore of marrying the heir to the Grae fortune and of her crumbling family, Alena wants Airie to become part of the sea with her: by drowning herself to become a mermaid. With revolution against the Finnders brewing in the town and her own brother being a part of it, Airie cannot leave with Alena either. However, Airie cannot live life with one foot in sea and one foot on shore, and life is the one thing that is constant never.
In the epic conclusion to the Devil's Deal series, Freya has one final chance to discover the full potential of her own power, and to use it to restore balance in the universe - once and for all. After the destruction caused by Roisin, Ferya and Torix come to terms with their losses and mistakes... And prepare for a final battle that will change everything.