Christian Thydell has been receiving anonymous threats since he began writing his novel The Mermaid. When one message,secreted within a bouquet of flowers, causes him to collapse at the launch party, crime writer Erica Falck is compelled to investigate. Erica's husband detective Patrik Hedström, meanwhile, is puzzled by the disappearance of Christian's friend Magnus Kjellner four months previously. When a body is found frozen in the sea near Fjallbacka, he has a murder enquiry on his hands.