Särsö gathers for the annual party in honor of the sea, but after Danne's death, far from everyone feels grateful. While old conflicts flare up during the party night, Johannes is drawn deeper and deeper into the obsession with the mermaid. When he sees how Helena is affected by her powers, Johannes's anxiety grows, and in the end he is forced to make a crucial decision.

Axelsson presses Krille for answers about his dead friend Danne, while Johannes is tormented by the guilt surrounding Helena. Old stories about Svärtan come to the surface and when the mermaid suddenly returns, Johannes is forced to make a crucial choice - at the same time that Axelsson comes dangerously close to the truth.