Simi prayed to the gods, once. Now she serves them as Mami Wata—a mermaid—collecting the souls of those who die at sea and blessing their journeys back home. But when a living boy is thrown overboard, Simi saves his life, going against an ancient decree. And punishment awaits those who dare to defy it. To protect the other Mami Wata, Simi must journey to the Supreme Creator to make amends. But something is amiss. There's the boy she rescued, who knows more than he should. And something is shadowing Simi, something that would rather see her fail. Danger lurks at every turn, and as Simi draws closer, she must brave vengeful gods, treacherous lands, and legendary creatures. Because if she doesn't, then she risks not just the fate of all Mami Wata, but also the world as she knows it.