The sea is close. We're close. And we will drown you all. Lucy can control the wind and water with a song, she can conquer kingdoms. Lucy has mastered the power and King Henry keeps her close, restoring England. She is his best ally and constantly works for him. And now he asks her to investigate an attempted murder: his people claim that they were almost killed... by a mermaid. The water is coming, people are trying to protect themselves from the water and the monsters that appear on the streets. As mistrust of Lucy's magic grows, the king hopes that Nat, Lucy's lover, can make things right. But Nat is cold towards Lucy. He confessed his love a year ago, and now she’s like a stranger to him. Lucy has to fight alone with powerful new magic. But then she hears an ominous song in the water... Does this mean that she is not the last Warbler?