Suddenly, Tristan's girlfriend dramas and swimming championship seem like distant worries as he discovers the truth: he's a Merman. Now Tristan must fight for his life, the lives of his friends, and his humanity (if he still wants it), while competing in a race for a throne as ancient as the gods. Like the seductive, duplicitous faeries of Wicked Lovely, these sirens of the deep have an agenda of their own.