Fish are mysteriously disappearing, starving the people in Angie Song's Alaskan hometown. Angie, an aspiring marine biologist and dock worker, enthusiastically joins the hunt to find out where the fish are gathering. When her family and the villagers discover that merfolk are responsible, they vow to destroy every last one. In the midst of the conflict, Angie faces off with a merman and fails to pull the trigger.

Inquisitive Mer-Prince Kaden is just as snarky as Angie, but he's willing to talk and stop the brutal massacring of his people. The two form a cautious alliance to broker peace between the humans and mer before any more of them die.

As tensions clash between the two races fighting to control the sea's resources, Angie and Kaden's forbidden relationship ignites. And as she learns about the mer's mysterious world and the reason why the fish are gone, Angie starts to question who the true monster is, and where her loyalties lie. Taking the wrong side means choosing between family and her job, or the man she's fallen for and the merfolk she's come to respect-or losing it all.