In the continuation of the story "Poseidon", Emma learns that her mother is the long-lost daughter of the sea king. Now the girl is going through a personal crisis: both for people she is a half-monster, and for the inhabitants of the depths of the sea she is an outcast. And according to the underwater law, all half-sirens must be executed. And this is not the worst thing. The return of Emma's mother sparks a feud between the families of Poseidon and Triton. Now Emma will have to decide whether to follow Galen's advice to lie low and hope for the best... or risk everything and reveal the secret of her gift in order to save a people alien to her.